Systems and methods for a stationary ct imaging system

ABSTRACT

Various methods and systems are provided for stationary CT imaging. In one embodiment, a modular imaging system comprises a plurality of distributed x-ray units releasably coupled to a plurality of detector arrays, with the plurality of distributed x-ray units and the plurality of detector arrays forming a self-supporting structure including a central opening shaped to receive a subject to be imaged. The modular imaging system may image the subject without rotation of the distributed x-ray units or detector arrays around the subject.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 63/036,162, titled “A TRANSPORTABLE AND AUTONOMOUS STATIONARY CTIMAGING SYSTEM,” and filed Jun. 8, 2020; U.S. Provisional PatentApplication No. 63/036,272, titled “AN UPRIGHT STATIONARY CT IMAGINGSYSTEM AND IMAGE RECONSTRUCTION FOR SAME,” and filed Jun. 8, 2020; U.S.Provisional Patent Application No. 63/036,203, titled “A DISTRIBUTEDX-RAY SOURCE FOR AN IMAGING SYSTEM,” and filed Jun. 8, 2020; U.S.Provisional Patent Application No. 63/039,071, titled “A STATIONARY CTIMAGING SYSTEM AND SCATTERED X-RAY RADIATION,” and filed Jun. 15, 2020;and U.S. Provisional Patent Application No. 63/039,181, titled “AMULTI-ENERGY STATIONARY CT IMAGING SYSTEM,” and filed Jun. 15, 2020. Theentire contents of each of the above-identified applications is herebyincorporated by reference for all purposes.

FIELD

Embodiments of the subject matter disclosed herein relate to computedtomography (CT) imaging, and more particularly to a stationary CTimaging system.

BACKGROUND

Computed tomography (CT) imaging systems enable fast, non-invasiveimaging of a variety of tissues, including bone, soft tissue, etc., aswell as high contrast detection that allows CT imaging systems tovisualize contrast agents. However, conventional CT imaging systems relyon complex and tightly controlled rotating gantries that support one ormore x-ray sources and one or more detector arrays. Accordingly,conventional CT imaging systems are expensive, large, heavy, anddifficult to install, which limits the environments in which CT imagingsystems may be utilized.

BRIEF DESCRIPTION

This summary introduces concepts that are described in more detail inthe detailed description. It should not be used to identify essentialfeatures of the claimed subject matter, nor to limit the scope of theclaimed subject matter.

In one aspect, a modular imaging system comprises a plurality ofdistributed x-ray units releasably coupled to a plurality of detectorarrays, with the plurality of distributed x-ray units and the pluralityof detector arrays forming a self-supporting structure including acentral opening shaped to receive a subject to be imaged. The modularimaging system may thus be assembled for imaging of subjects inlocations that may be difficult to accommodate larger imaging systemsand/or less portable imaging systems. Additionally, the modular imagingsystem is configured for stationary imaging of a subject withoutrotation of the distributed x-ray units and the detector arrays aroundthe subject, which may reduce a cost of the modular imaging systemrelative to conventional imaging systems that include a rotating gantryand further increase the portability and/or compactness of the modularimaging system.

It should be understood that the brief description above is provided tointroduce in simplified form a selection of concepts that are furtherdescribed in the detailed description. It is not meant to identify keyor essential features of the claimed subject matter, the scope of whichis defined uniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be better understood from reading thefollowing description of non-limiting embodiments, with reference to theattached drawings, wherein below:

FIG. 1 shows a block schematic diagram of an exemplary imaging system,according to an embodiment.

FIG. 2 shows a perspective view of a modular stationary imaging system,according to an embodiment.

FIG. 3 shows a front view of the modular stationary imaging system ofFIG. 2.

FIG. 4 shows a perspective view of an upright stationary imaging system,according to an embodiment.

FIG. 5 shows a front view of the upright stationary imaging system ofFIG. 4.

FIG. 6 shows a side view of a target of an x-ray emitter, according toan embodiment.

FIG. 7 shows a side view of another target of an x-ray emitter,according to an embodiment.

FIG. 8 shows schematically shows an electron beam, according to anembodiment.

FIG. 9 shows an insulator for an x-ray emitter, according to anembodiment.

FIG. 10 shows another insulator for an x-ray emitter, according to anembodiment.

FIG. 11 shows another insulator for an x-ray emitter, according to anembodiment.

FIG. 12 shows another insulator for an x-ray emitter, according to anembodiment.

FIG. 13 shows schematically shows an interface for a high voltagegenerator and x-ray tubes.

FIG. 14 shows schematically shows another view of the interface of FIG.13.

FIG. 15 shows a side view of a segment of a high voltage distributionsystem, according to an embodiment.

FIG. 16 schematically shows a flat connector for a high voltagedistribution system, according to an embodiment.

FIG. 17 shows a front view of another high voltage distribution system,according to an embodiment.

FIG. 18 shows an enlarged side view of interlocking sections of the highvoltage distribution system of FIG. 17.

FIG. 19 shows a connector and a connection of a high voltagedistribution system in an uncoupled configuration, according to anembodiment.

FIG. 20 shows the connector and connection of FIG. 19 in a coupledconfiguration.

FIG. 21 shows various connection geometries of connectors andconnections of a high voltage distribution system, according to anembodiment.

FIG. 22 shows a first configuration of a multi-modal imaging system,according to an embodiment.

FIG. 23 shows a second configuration of a multi-modal imaging system,according to an embodiment.

FIG. 24 shows a third configuration of a multi-modal imaging system,according to an embodiment.

FIG. 25 schematically shows a first exemplary single energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 26 schematically shows a second exemplary single energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 27 schematically shows a third exemplary single energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 28 schematically shows a fourth exemplary single energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 29 schematically shows a fifth exemplary single energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 30 schematically shows a sixth exemplary single energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 31 schematically shows a first exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 32 schematically shows a second exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 33 schematically shows a third exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 34 schematically shows a fourth exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 35 schematically shows a fifth exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 36 schematically shows a sixth exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIG. 37 schematically shows a seventh exemplary multi-energy distributedx-ray source and detector configuration for an imaging unit, accordingto an embodiment.

FIGS. 38A and 38B schematically show an eighth exemplary multi-energydistributed x-ray source and detector configuration for an imaging unit,according to an embodiment.

FIGS. 39A and 39B schematically show a ninth exemplary multi-energydistributed x-ray source and detector configuration for an imaging unit,according to an embodiment.

FIG. 40 schematically shows a first exemplary distributed x-ray sourceand detector configuration for an imaging unit that includes multipledifferent detector types, according to an embodiment.

FIG. 41 schematically shows a second exemplary multi-detector typedistributed x-ray source and detector configuration for an imaging unitthat includes multiple different detector types, according to anembodiment.

FIGS. 42A and 42B schematically show x-ray beam truncation for animaging unit, according to an embodiment.

FIG. 43 schematically shows an x-ray source and detector configurationfor an imaging unit that includes a first exemplary pre-patientcollimator, according to an embodiment.

FIG. 44 schematically shows an x-ray source and detector configurationfor an imaging unit that includes a second exemplary pre-patientcollimator, according to an embodiment.

FIG. 45 schematically shows adjusting a fan angle of a focal spot forscatter measurements in an imaging unit, according to an embodiment.

FIG. 46 schematically shows a multi-layer aperture device for an imagingunit, according to an embodiment.

FIG. 47 schematically shows using primary beam modulation for scattermeasurements in an x-ray source and detector configuration of an imagingunit, according to an embodiment.

FIG. 48 schematically shows scatter measurements in an x-ray source anddetector configuration of an imaging unit, according to an embodiment.

FIG. 49 schematically shows using lead blockers for scatter measurementsin an x-ray source and detector configuration of an imaging unit,according to an embodiment.

FIG. 50 schematically shows non-uniform view sampling in an imagingunit, according to an embodiment.

FIG. 51 is a high-level flow chart illustrating a method for performingCT scans using a stationary CT imaging system, according to anembodiment.

FIG. 52 is a flow chart illustrating a method for performing a singleenergy CT scan using a stationary CT imaging system, according to anembodiment.

FIG. 53 is a flow chart illustrating a method for reconstructing imagesfrom a single energy CT scan performed on a stationary CT imagingsystem, according to an embodiment.

FIG. 54 is a flow chart illustrating a method for performing amulti-energy CT scan using a stationary CT imaging system, according toan embodiment.

FIG. 55 is a flow chart illustrating a method for reconstructing imagesfrom a multi-energy CT scan performed on a stationary CT imaging system,according to an embodiment.

FIG. 56 schematically illustrates a generative adversarial network thatmay be used in image reconstruction, according to an embodiment.

FIG. 57 schematically illustrates an iterative reconstruction approachthat may be used for image reconstruction, according to an embodiment.

FIGS. 2-7 and 9-21 are shown approximately to scale, although otherrelative dimensions may be used, if desired.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described, by way ofexample, with reference to the FIGS. 1-57, which relate to variousembodiments for stationary computed tomography (CT) imaging systems.

FIG. 1 illustrates an exemplary imaging system 100 configured for CTimaging. Particularly, the imaging system 100 is configured to image asubject 127. Subject 127 may be a patient, an inanimate object, one ormore manufactured parts, and/or foreign objects such as dental implants,stents, and/or contrast agents present within the body. In oneembodiment, the imaging system 100 includes a frame 102, which in turn,may further include at least one distributed x-ray source unit 104configured to project x-ray radiation for use in imaging the subject 127supported by a support surface 135. Specifically, the distributed x-raysource unit 104 is configured to project x-ray radiation beams 149towards a detector array 147 positioned on the opposite side of theframe 102, with the detector array 147 including a plurality of x-raydetectors (e.g., detector cells) such as a detector 103, a detector 105,a detector 107, etc. Although FIG. 1 depicts only a single distributedx-ray source unit 104 and a single detector array 147, in certainembodiments, multiple distributed x-ray source units and detector arraysmay be employed to project x-ray radiation beams for acquiringprojection data. Although FIG. 1 depicts the detector array 147 asincluding three detectors (e.g., the detector 103, the detector 105, andthe detector 107), in some embodiments, the detector array 147 and/orother detector arrays may include a different number of detectors (e.g.,four, five, ten, etc.). Further, although FIG. 1 depicts the distributedx-ray source unit 104 as including three individual x-ray emitters suchas an emitter 106, an emitter 108, and an emitter 109, in someembodiments, the distributed x-ray source unit 104 and/or otherdistributed x-ray source units may include a different number of x-rayemitters (e.g., four, five, ten, etc.).

The detectors of the detector array 147 sense the x-ray radiation beams149 that pass through the subject 127 to acquire correspondingprojection data. In some embodiments, one or more of the detectors ofthe imaging system 100 (e.g., the detectors of detector array 147) maybe a different type of detector relative to other detectors of theimaging system 100. For example, the detectors of the detector array 147(e.g., the detector 103, the detector 105, the detector 107, etc.) maybe energy-integrating detectors, energy-discriminating detectors,photon-counting detectors, multiple resolution detectors (e.g., higherresolution detectors or lower resolution detectors), multiple dimensiondetectors (e.g., larger detectors covering a larger area or smallerdetectors covering a smaller area), scintillator-based detectors,direct-conversion detectors, etc., or some combination thereof (e.g.,the detector 103 may be an energy-integrating detector and the detector105 may be a photon-counting detector, the detector 105 may be a lowerresolution detector and the detector 107 may be a higher resolutiondetector, etc.). In some embodiments, the distributed x-ray source unit104 may enable dual-energy gemstone spectral imaging (GSI) by rapid peakkilovoltage (kVp) switching. In some embodiments, the x-ray detectorsemployed are photon-counting detectors that are capable ofdifferentiating x-ray photons of different energies. In otherembodiments, two sets of x-ray sources and detectors are used togenerate dual-energy projections, with one set at a low kVp and theother at a high kVp. It may thus be appreciated that the methodsdescribed herein may be implemented with single energy acquisitiontechniques as well as dual (or multiple) energy acquisition techniques.

Each x-ray emitter of the distributed x-ray source unit 104 includes arespective anode and a respective cathode. For example, the emitter 106includes an anode 111 and a cathode 113, the emitter 108 includes ananode 115 and a cathode 117, and the emitter 109 includes an anode 121and a cathode 119. Electrons emitted by the cathodes (e.g., resultingfrom energization of the cathodes) may be intercepted by the respectiveanodes. Electrons intercepted by the anodes may release energy in theform of x-rays, with the x-rays being directed toward the detector array147. An area of each anode surface that receives the electrons from therespective cathode and forms the emitted x-rays may be referred toherein as a “focal spot.” In some embodiments, one or more of the anodesmay be rotating anodes configured to rotate around an axis extendingbetween the anodes and respective cathodes (e.g., the anode 111 mayrotate around an axis extending between the anode 111 and cathode 113).The rotation of the anodes may reduce a heating of the anodes by theelectrons emitted by the respective cathodes (e.g., rotation of theanodes may increase an effective surface area of the anodes coming intocontact with the electrons emitted by the cathodes). However, in otherembodiments, the anodes may not be rotating anodes.

In certain embodiments, the imaging system 100 further includes an imageprocessor unit 151 with an image reconstructor 130 configured toreconstruct images of a target volume of the subject 127 using aniterative or analytic image reconstruction method. For example, theimage reconstructor 130 may use an analytic image reconstructionapproach such as filtered back projection (FBP) to reconstruct images ofa target volume of the patient. As another example, the imagereconstructor 130 may use an iterative image reconstruction approachsuch as advanced statistical iterative reconstruction (ASIR), conjugategradient (CG), maximum likelihood expectation maximization (MLEM),model-based iterative reconstruction (MBIR), and so on to reconstructimages of a target volume of the subject 127. As described furtherherein, in some examples, the image reconstructor 130 may use both ananalytic image reconstruction approach such as FBP in addition to aniterative image reconstruction approach.

In some CT imaging system configurations, an x-ray source projects acone-shaped x-ray radiation beam which is collimated to lie within anX-Y-Z plane of a Cartesian coordinate system and generally referred toas an “imaging plane.” The x-ray radiation beam passes through an objectbeing imaged, such as the patient or subject. The x-ray radiation beam,after being attenuated by the object, impinges upon an array of detectorelements. The intensity of the attenuated x-ray radiation beam receivedat the detector array is dependent upon the attenuation of a radiationbeam by the object. Each detector of the detector array produces aseparate electrical signal that is a measurement of the x-ray beamattenuation at the detector location. The attenuation measurements fromall the detectors are acquired separately to produce a transmissionprofile.

In the examples described herein, the distributed x-ray source units andthe detector arrays are arranged within an imaging plane around theobject to be imaged. In this configuration, beams of x-ray radiationfrom the distributed x-ray source units intersect the object (e.g., thesubject 127) at different angles, with the beams being intercepted bythe detectors of the detector arrays. For example, a given beam of x-rayradiation may pass through the subject 127 and may be attenuated by thesubject 127, and the attenuated beam may then be intercepted by thedetectors of the detector arrays. x-ray radiation attenuationmeasurements (e.g., projection data) acquired by a given detector may beassociated with a given beam of x-ray radiation intercepted by thedetector at a given angle and may be referred to herein as a “view”(e.g., each beam intercepted by the detector may be projected toward thedetector at a different angle and may correspond to a different view). A“scan” of the object includes a set of views made at different angles,or view angles. For example, a scan of the object may include one ormore views acquired by a first detector and one or more views acquiredby a second detector, where an angle of a given beam of x-ray radiationto the first detector may be different than an angle of the given beamto the second detector. The term “view” as used herein is not limited tothe use as described above with respect to projection data from oneframe angle. The term “view” is used to mean one data acquisitionwhenever there are multiple data acquisitions from different angles.

The projection data is processed to reconstruct an image thatcorresponds to a two-dimensional slice taken through the object or, insome examples where the projection data includes multiple views orscans, a three-dimensional rendering of the object. One method forreconstructing an image from a set of projection data is referred to inthe art as the filtered back projection (FBP) technique. Transmissionand emission tomography reconstruction techniques also includestatistical iterative methods such as maximum likelihood expectationmaximization (MLEM) and ordered-subsets expectation-reconstructiontechniques as well as iterative reconstruction techniques. This processconverts the attenuation measurements from a scan into integers called“CT numbers” or “Hounsfield units,” which are used to control thebrightness of a corresponding pixel on a display device.

To reduce the total scan time, a “helical” scan may be performed. Toperform a “helical” scan, the patient may be moved while the data forthe prescribed number of slices is acquired. Such a system generates asingle helix from a cone beam helical scan. The helix mapped out by thecone beam yields projection data from which images in each prescribedslice may be reconstructed.

As used herein, the phrase “reconstructing an image” is not intended toexclude embodiments of the present disclosure in which data representingan image is generated but a viewable image is not. Therefore, as usedherein, the term “image” broadly refers to both viewable images and datarepresenting a viewable image. However, many embodiments generate (orare configured to generate) at least one viewable image.

In some embodiments, each detectors array, such as detector array 147,is fabricated in a multi-slice configuration including a plurality ofrows of detectors (e.g., the detector 103, the detector 105, thedetector 107, etc.). In such a configuration, one or more additionalrows of the detectors are arranged in a parallel configuration foracquiring the projection data.

As the distributed x-ray source unit 104 and the detector array 147collects data of the attenuated x-ray beams, the data collected by thedetector array 147 undergoes pre-processing and calibration to conditionthe data to represent the line integrals of the attenuation coefficientsof the scanned subject 127. The processed data are commonly calledprojections.

In some examples, the individual detectors of the detector array 147(e.g., the detector 103, the detector 105, the detector 107, etc.) maybe photon-counting detectors which register the interactions ofindividual photons into one or more energy bins. It should beappreciated that the methods described herein may also be implementedwith energy-integrating detectors.

The acquired sets of projection data may be used for basis materialdecomposition (BMD). During BMD, the measured projections are convertedto a set of material-density projections. The material-densityprojections may be reconstructed to form a pair or a set ofmaterial-density map or image of each respective basis material, such asbone, soft tissue, and/or contrast agent maps. The density maps orimages may be, in turn, associated to form a volume rendering of thebasis material, for example, bone, soft tissue, and/or contrast agent,in the imaged volume.

Once reconstructed, the basis material image produced by the imagingsystem 100 reveals internal features of the subject 127, expressed inthe densities of two basis materials. The density image may be displayedto show these features. In traditional approaches to diagnosis ofmedical conditions, such as disease states, and more generally ofmedical events, a radiologist or physician would consider a hard copy ordisplay of the density image to discern characteristic features ofinterest. Such features might include lesions, sizes and shapes ofparticular anatomies or organs, and other features that would bediscernable in the image based upon the skill and knowledge of theindividual practitioner.

In one embodiment, the imaging system 100 includes a control mechanism153 to control movement of components such as the support surface 135and the operation of the distributed x-ray source unit 104. The controlmechanism 153 may further include an x-ray controller 110 configured toprovide power and timing signals to the distributed x-ray source unit104. Additionally, the control mechanism 153 may include a supportsurface motor controller 126 configured to control a translation speedand/or position of the support surface 135 based on a desired imagingconfiguration.

In certain embodiments, the control mechanism 153 further includes adata acquisition system (DAS) 155 configured to sample analog datareceived from the detectors of the detector array 147 and convert theanalog data to digital signals for subsequent processing. The DAS 155may be further configured to selectively aggregate analog data from asubset of the detectors of the detector array 147 into so-calledmacro-detectors, as described further herein. The data sampled anddigitized by the DAS 155 is transmitted to a computer or computingdevice 116. In one example, the computing device 116 stores the data ina storage device or mass storage 118. The mass storage 118, for example,may include a hard disk drive, a floppy disk drive, a compactdisk-read/write (CD-R/W) drive, a Digital Versatile Disc (DVD) drive, aflash drive, and/or a solid-state storage drive.

Additionally, the computing device 116 provides commands and parametersto one or more of the DAS 155, the x-ray controller 110, and the supportsurface motor controller 126 for controlling system operations such asdata acquisition and/or processing. In certain embodiments, thecomputing device 116 controls system operations based on operator input.The computing device 116 receives the operator input, for example,including commands and/or scanning parameters via an operator console120 operatively coupled to the computing device 116. The operatorconsole 120 may include a keyboard (not shown) or a touchscreen to allowthe operator to specify the commands and/or scanning parameters.

Although FIG. 1 illustrates only one operator console 120, more than oneoperator console may be coupled to the imaging system 100, for example,for inputting or outputting system parameters, requesting examinations,plotting data, and/or viewing images. Further, in certain embodiments,the imaging system 100 may be coupled to multiple displays, printers,workstations, and/or similar devices located either locally or remotely,for example, within an institution or hospital, or in an entirelydifferent location via one or more configurable wired and/or wirelessnetworks such as the Internet and/or virtual private networks, wirelesstelephone networks, wireless local area networks, wired local areanetworks, wireless wide area networks, wired wide area networks, etc.

In one embodiment, for example, the imaging system 100 either includes,or is coupled to, a picture archiving and communications system (PACS)124. In an exemplary implementation, the PACS 124 is further coupled toa remote system such as a radiology department information system,hospital information system, and/or to an internal or external network(not shown) to allow operators at different locations to supply commandsand parameters and/or gain access to the image data.

The computing device 116 uses the operator-supplied and/orsystem-defined commands and parameters to operate support surface motorcontroller 126, which in turn, may control a position of the supportsurface 135. Specifically, the support surface motor controller 126 maymove the support surface 135 for appropriately positioning the subject127 within an opening 125 for acquiring projection data corresponding tothe target volume of the subject 127.

As previously noted, the DAS 155 samples and digitizes the projectiondata acquired by the detectors of the detector array 147. Subsequently,the image reconstructor 130 uses the sampled and digitized x-ray data toperform high-speed reconstruction. Although FIG. 1 illustrates the imagereconstructor 130 as a separate entity, in certain embodiments, theimage reconstructor 130 may form part of the computing device 116.Alternatively, the image reconstructor 130 may be absent from theimaging system 100 and instead the computing device 116 may perform oneor more functions of the image reconstructor 130. Moreover, the imagereconstructor 130 may be located locally or remotely, and may beoperatively connected to the imaging system 100 using a wired orwireless network. Particularly, one exemplary embodiment may usecomputing resources in a “cloud” network cluster for the imagereconstructor 130.

In one embodiment, the image reconstructor 130 stores the imagesreconstructed in the mass storage 118. Alternatively, the imagereconstructor 130 may transmit the reconstructed images to the computingdevice 116 for generating useful patient information for diagnosis andevaluation. In certain embodiments, the computing device 116 maytransmit the reconstructed images and/or the patient information to adisplay or display device 132 communicatively coupled to the computingdevice 116 and/or the image reconstructor 130. In some embodiments, thereconstructed images may be transmitted from the computing device 116 orthe image reconstructor 130 to the mass storage 118 for short-term orlong-term storage.

In some embodiments, the imaging system 100 may include a voltageswitcher 137 configured to control energization of emitters of theimaging system 100 (e.g., the emitter 106, the emitter 108, the emitter109, etc.). The voltage switcher 137 may include a generator array 139comprising one or more generators, such as a generator 141, a generator143, etc. Although FIG. 1 shows the generator array 139 including twogenerators, in some embodiments, the voltage switcher and generatorarray may include a different number of generators (e.g., one, three,four, etc.). In some examples, one or more of the generators may bedynamic resonance energy-recovery (DRER) generators configured torecover electrical charge stored on the capacitances of the imagingsystem 100 (e.g., charge stored on cables, anodes, etc. of the imagingsystem 100).

The voltage switcher 137 is electronically coupled to an x-ray powersource 145. In some embodiments, the x-ray power source 145 may be astationary power source, such as an electrical power supply of a medicalfacility housing the imaging system 100. In other embodiments, the x-raypower source 145 may be a mobile electrical power source, such as abattery or an array of batteries. The x-ray power source 145 isconfigured to provide electrical power to the emitters of the imagingsystem 100 via the x-ray controller 110 and/or the voltage switcher 137.For example, in embodiments that do not include the voltage switcher137, the x-ray emitters of the imaging system 100 may receive electricalpower (e.g., electrical current) from the x-ray power source 145 via thex-ray controller 110 (e.g., the x-ray controller 110 may be configuredto control an energization timing and/or energization amount of thex-ray emitters). In other embodiments, the x-ray emitters may receiveelectrical power from the x-ray power source 145 via one or both of thex-ray controller 110 and the voltage switcher 137. For example, thex-ray controller 110 may control an operating mode of the distributedx-ray source unit 104 (e.g., adjust the distributed x-ray source unit104 between an “ON” mode wherein one or more emitters of the distributedx-ray source unit 104 are energized, and an “OFF” mode in which none ofthe emitters of the distributed x-ray source unit 104 are energized),and the voltage switcher 137 may control an amount of energization ofone or more of the emitters independent of the other emitters (e.g., thevoltage switcher 137 may control a voltage of the emitter 106 and theemitter 108 separately, such that the emitter 106 may be operated at afirst voltage and the emitter 108 may be operated at a different, secondvoltage).

The voltage switcher 137 may control the energization of the x-rayemitters by adjusting the amount and/or timing of the energization toindividual emitters. As one example, one or more emitters of thedistributed x-ray source unit 104 may be configured to operate at adifferent voltage relative to other emitters of the distributed x-raysource unit 104 (e.g., the emitter 106 may be configured to operate at adifferent voltage compared to the emitter 108). The generator 141 may beconfigured to energize one or more of the emitters of the distributedx-ray source unit 104 at a first voltage (e.g., 0 kVp, with therespective cathode maintained at −50 kVp), and the generator 143 may beconfigured to energize one or more of the emitters of the distributedx-ray source unit 104 at a different, second voltage (e.g., 50 kVp, withthe respective cathode maintained at −50 kVp). As another example, theanodes of the emitters may be maintained at a given voltage (e.g., 90kVp), and the first generator 141 and/or the second generator 143 mayadjust the voltage of each respective cathode in order to adjust theelectrical potential difference between the anodes and cathodes, wherethe adjustment for a given emitter may be different compared to at leastone other emitter (e.g., the anodes of both of the emitter 106 and theemitter 108 may be maintained at 90 kVp, and the voltage switcher mayadjust the cathodes between −50 kVp and 0 kVp independently of eachother, as one example).

As another example, one or more of the emitters of the distributed x-raysource unit 104 may be configured to operate in different energizationmodes, with the voltage switcher 137 configured to adjust the emittersbetween the different energization modes (e.g., the emitter 106 may beconfigured to operate in a higher, first voltage mode or a lower, secondvoltage mode, with the voltage switcher 137 configured to adjust theemitter 106 between the first voltage mode and the second voltage mode).For example, in configurations in which one or more of the generators isconfigured as a DRER generator as described above, a switching speed(e.g., adjustment speed) of the emitters between the differentenergization modes may be increased. As another example, one or more ofthe emitters may include two or more anodes, and the anodes may beconfigured to operate at different voltages. The two or more anodes mayintercept electrons emitted by a single cathode, or in some examples theone or more emitters including the two or more anodes may include two ormore respective cathodes. As another example, the imaging system 100includes the distributed x-ray source unit 104 along with one or moreadditional distributed x-ray source units. The emitters of differentdistributed x-ray source units may be configured to operate at differentvoltages (e.g., the distributed x-ray source unit 104, which may bereferred to as a first distributed x-ray source unit, includes emittersthat may be operated at a first voltage, and a second distributed x-raysource unit of the imaging system may include emitters configured tooperate at a different, second voltage).

In some examples, one or more of the emitters of the distributed x-raysource units of the imaging system 100 (e.g., distributed x-ray sourceunit 104) may be sized differently relative to other emitters of theimaging system 100. For example, the emitter 106 may be larger than theemitter 108 (e.g., the anode 111 may be larger than the anode 115).Larger emitters (e.g., focal spots) may increase a signal-to-noise ratioof images acquired by the imaging system 100. However, smaller emittersmay increase a spatial resolution of the images acquired by the imagingsystem 100. Images acquired by emitters having the larger size may bereconstructed into one image, and images acquired by emitters having thesmaller size may be reconstructed into a different, second image. Theresulting low-noise and high-resolution images may then be combinedusing a deep learning network, in some examples.

In some examples, one or more of the emitters of the distributed x-raysource unit 104 may be formed of two or more different materials, whereeach material is configured to emit x-ray radiation at different energylevels (e.g., different frequencies). For example, the emitter 106 mayinclude the cathode 113 configured to emit electrons to the anode 111,where the anode 111 includes at least two different materials configuredto intercept the electrons emitted by the cathode 113. During conditionsin which the electrons are intercepted by the portion of the anode 111including a first material, the anode 111 may emit x-ray radiation witha first energy (e.g., a first wavelength), and during conditions inwhich the electrons are intercepted by a portion of the anode 111including a different, second material, the anode 111 may emit x-rayradiation with a different, second energy (e.g., a second wavelength).In some examples, the anode 111 may be rotated via the x-ray controller110 in order to control whether the electrons emitted by the cathode 113are intercepted by the portion of the anode 111 formed by the firstmaterial or the portion of the anode 111 formed by the second materialin order to control the energy of the x-ray radiation emitted by theanode 111. Although the emitter 106 is described above as an example, inother examples one or more of the emitter 108, the emitter 109, or otheremitters of the imaging system 100 may include a similar configuration(e.g., a configuration including an anode having two or more materialsthat may intercept electrons emitted by a respective cathode). In someexamples, the anodes may include other materials such as one or morediamond layers and/or phase-change materials, in addition to thematerials described above.

As described above, the imaging system 100 includes the distributedx-ray source unit 104 and may further include additional distributedx-ray source units. In some embodiments, the x-ray emitters of a givendistributed x-ray source unit may be maintained at a different voltagerelative to the x-ray emitters of at least one other distributed x-raysource unit. For example, the emitter 106, the emitter 108, and theemitter 109 of the distributed x-ray source unit 104 may each bemaintained at a first voltage, and emitters of a second distributedx-ray source unit may be maintained at a different, second voltage. Inembodiments in which the imaging system includes four or moredistributed x-ray source units, distributed x-ray source units that arearranged adjacent to each other may have emitters that are maintained atdifferent voltages. For example, in a configuration that includes fourdistributed x-ray source units arranged around a central axis of theimaging system, a first distributed x-ray source unit may be arranged ata first position, a second distributed x-ray source unit may be arrangedat a second position in a clockwise direction around the central axisfrom the first distributed x-ray source unit, a third distributed x-raysource unit may be arranged at a third position in the clockwisedirection around the central axis from the second distributed x-raysource unit, and a fourth distributed x-ray source unit may be arrangedat a fourth position in the clockwise direction around the central axisfrom the third distributed x-ray source unit. The first distributedx-ray source unit and the third distributed x-ray source unit may eachinclude x-ray emitters maintained at a first voltage (e.g., 90 kVp), andthe second distributed x-ray source unit and fourth distributed x-raysource unit may each include x-ray emitters maintained at a secondvoltage (e.g., 140 kVp). As another example, the imaging system mayinclude a first plurality of distributed x-ray source units arrangedaround the central axis (e.g., encircling the central axis) at a firstlocation along the central axis, and a second plurality of distributedx-ray source units arranged around the central axis at a different,second location along the central axis (e.g., where the second locationis spaced apart from the first location). The first plurality ofdistributed x-ray source units may include emitters maintained at thefirst voltage, and the second plurality of distributed x-ray sourceunits may include emitters maintained at the second voltage. Otherexamples are possible.

The imaging system 100 includes the frame 102 and an imaging unit 123,where the imaging unit 123 may comprise a gantry having the opening 125and includes the distributed x-ray source units (e.g., the distributedx-ray source unit 104) and the detectors arrays (e.g., the detectorarray 147). In some embodiments (e.g., similar to the example describedbelow with reference to FIGS. 2-3), the imaging unit 123 may be astationary imaging unit 123 configured to image the subject 127 withoutrotation or translation. For example, the imaging unit 123 may include aplurality of distributed x-ray source units and a plurality of detectorarrays arranged around a central axis 157. The subject 127 to be imagedmay be positioned along the central axis 157 such that the subject 127is encircled by the distributed x-ray source units and the detectorarrays, and the distributed x-ray source units may project x-ray beamsthrough the subject 127 toward the detectors arrays for imaging thesubject 127 without moving (e.g., rotating, translating, etc.) relativeto the subject 127. The imaging system 100 may reconstruct images of thesubject 127 via the image reconstructor 130 according to the methodsdescribed herein (e.g., via a deep learning network).

In some embodiments (e.g., similar to the example described below withreference to FIGS. 4-5), the imaging system may include the motorcontroller 112 configured to adjust a translation of the imaging unit123. For example, the subject 127 to be imaged may be arrangedvertically in an upright position (e.g., with a base, or feet, of thesubject 127 arranged toward a ground surface upon which the imagingsystem 100 sits, and with a top, or head, of the subject 127 arrangedaway from the ground surface), and the motor controller 112 maytranslate the imaging unit 123 in the vertical direction during imagingof the subject 127 (e.g., during a scan of the subject 127). Althoughthe motor controller 112 may translate the imaging unit 123, the motorcontroller 112 does not rotate the imaging unit 123. Moving the imagingunit 123 via the motor controller 112 may be performed during a chestscan of the subject 127, for example, and may increase an amount of thesubject 127 imaged by the imaging system 100. In order to provide for awide angle range of imaging of the subject 127 (e.g., 180 degrees aroundthe subject, 270 degrees around the subject, 360 degrees around thesubject, etc.) without rotation of the imaging unit 123, the distributedx-ray source units and the detectors of the imaging system are arrangedaround the axis of translation of the imaging unit 123. The imagereconstructor 130 may provide views of the subject 127 through the wideangle range using the images acquired by the detectors according to themethods described herein (e.g., via a deep learning network).

In some embodiments, the selection and orientation of the distributedx-ray source units and detectors may be based on an anatomy of thesubject 127 to be imaged. For example, the imaging system 100 may beconfigured with the distributed x-ray source units and detectors in anarrangement providing increased imaging quality for imaging a particularanatomical feature of the subject 127 (e.g., chest, head, etc.). As oneexample, the distributed x-ray source units and detectors may bearranged to provide increased imaging quality for imaging of the chestof the subject 127 by reducing distortion resulting from an inward andoutward motion of the chest as the patient breathes. As another example,the distributed x-ray source units and detectors may be arranged toprovide increased imaging quality for imaging of the head of the patientby reducing distortion resulting from a side-to-side movement of thehead of the subject 127. In yet other examples, the distributed x-raysource units and detectors may be arranged to reduce a power consumptionof the imaging system 100 (e.g., reduce a path length between thedistributed x-ray source units and the respective detectors). As yetanother example, the distributed x-ray source units and detectors may bearranged to reduce an x-ray dosage to particular anatomical features(e.g., reduce an amount of x-rays directed toward posterior features ofthe subject while imaging anterior features of the subject). In someexamples, the spacing and positioning of the x-ray emitters and thedetectors may be configured to increase a sampling density of theimaging system 100 by interlacing conjugate x-ray beams.

The imaging system 100 may further include a plurality of componentsarranged between the distributed x-ray source units (e.g., thedistributed x-ray source unit 104) and the detector arrays (e.g., thedetector array 147), with the components configured to adjust one ormore characteristics of the beams of x-rays emitted by the distributedx-ray source units and/or received by the detectors of the detectorarrays. For example, imaging system 100 may include a filter array 129,where the filter array 129 comprises one or more filters configured toadjust an energy of the x-ray beams emitted by the distributed x-raysource units. As one example, the filter array 129 may include a firstfilter configured to filter x-ray energy in a first range emitted by thedistributed x-ray source units (e.g., below 50 keV). In some examples,the filter array 129 may include one or more additional filters, such asa second filter configured to filter x-ray energy in a second rangeemitted by the distributed x-ray source units (e.g., below 70 keV). Insome examples, the filters of the filter array 129 may be positioned tofilter x-ray beams emitted by pre-determined emitters of the imagingsystem (e.g., the filters of the filter array 129 may filter all of thex-ray beams emitted by the emitters or only x-ray beams emitted by apre-determined set of the emitters). As one example, the filters of thefilter array 129 may be configured to filter the beams of x-rayradiation emitted by the emitters of the distributed x-ray source unit104 and may not be configured to filter beams of x-ray radiation emittedby other emitters of other distributed x-ray source units of the imagingsystem. As another example, the filters may be configured to filterbeams of x-ray radiation emitted by one or more emitters of thedistributed x-ray source unit 104 and may be configured to not filterbeams of x-ray radiation emitted by at least one emitter of thedistributed x-ray source unit 104.

In yet other examples, a position of the filter array 129 may beadjustable in order to adjust which emitters of the imaging system arefiltered by the filters of the filter array. For example, the filterarray 129 may be adjustable from a first position in which beams ofx-ray radiation emitted by the emitter 106 and the emitter 109 arefiltered by the filters of the filter array 129 (e.g., a position inwhich the filters of the filter array absorb x-rays emitted by theemitter 106 and emitter 109 at a particular energy range) to a secondposition in which beams of x-ray radiation emitted by the emitter 106and the emitter 109 are not filtered by the filters of the filter array129. As another example, a given emitter of the imaging system may befiltered by either a first filter or a second filter of the filter array129, with the filter array 129 being adjustable to arrange either orboth of the first filter or the second filter into position to filterthe x-ray beams emitted by the given emitter. In some embodiments, thefilter array may be arranged on an annulus, and the annulus may beconfigured to rotate to provide different filtration characteristics fordifferent emitters, similar to the examples described further below.

The imaging system 100 may include an anti-scatter grid 131 in someembodiments. The anti-scatter grid 131 is configured to reduce an amountof scattered x-ray radiation intercepted by the detectors. For example,the emitter 106 may emit a beam of x-ray radiation in the direction ofthe detector 107. The anti-scatter grid 131 may be configured to permitx-ray radiation projected from the emitter 106 directly toward thedetector 107 to be intercepted by the detector 107, while x-rayradiation scattered in directions not directly toward the detector 107may be absorbed by the anti-scatter grid 131. In this configuration, theanti-scatter grid 131 may intercept scattered x-ray radiation andincrease an imaging quality of the imaging system 100. In some examples,the anti-scatter grid 131 may be rotatable relative to the detectors inorder to adjust a radiation absorbing characteristic of the anti-scattergrid 131 (e.g., to adjust the direction in which x-ray radiation maypass through the anti-scatter grid 131 to the detectors). In someexamples, the anti-scatter grid 131 may include a plurality ofpartitions and may be configured to permit x-ray radiation to passbetween adjacent partitions in directions parallel with the adjacentpartitions. The positions of the partitions may be individuallyadjustable (e.g., via the control mechanism 153) in order to control thedirection at which x-ray radiation may pass through the anti-scattergrid 131 for interception by the detectors.

The imaging system 100 may include a multi-layer aperture device 133configured to control the direction of x-ray radiation intercepted bythe detectors. The multi-layer aperture device 133 may be included inaddition to the anti-scatter grid 131 described above, or the imagingsystem 100 may include the multi-layer aperture device 133 without theanti-scatter grid 131. The multi-layer aperture device 133 may include aplurality of rows (e.g., layers) of partitions, where the partitions maybe similar to the partitions included by the anti-scatter grid 131.However, each row of partitions may be rotatable and/or translatableindependently of each other row of partitions. For example, a first rowof partitions may initially be aligned with a second row of partitions(e.g., each partition of the first row may be arranged parallel andalong a same axis as a respective partition of the second row). Thepartitions of the first row may be shifted (e.g., translated) togetherrelative to the partitions of the second row in order to adjust analignment of openings (e.g., apertures) formed between the partitions ofthe first row with openings formed between the partitions of the secondrow.

Adjusting the alignment of the openings may adjust a direction at whichx-ray radiation may pass through the multi-layer aperture device 133,similar to the examples described further below. For example, in a firstconfiguration, the multi-layer aperture device 133 may allow x-rayradiation to pass through the openings of the multi-layer aperturedevice 133 in a first direction at a first angle (e.g., 0 degrees)relative to an axis extending between a given emitter and a givendetector, with the multi-layer aperture device 133 arranged between thegiven emitter and the given detector. In a second configuration, themulti-layer aperture device 133 may allow x-ray radiation to passthrough the openings in a second direction at a second angle (e.g., 30degrees) relative to the axis extending between the given emitter andthe given detector while blocking x-ray radiation projected in the firstdirection. Other configurations (e.g., other angles) are possible. Themulti-layer aperture device 133 may thus control the direction of x-rayradiation intercepted by the detectors (e.g., in order to reduceabsorption of scattered radiation by the detectors).

As described above, the imaging unit 123 of the imaging system 100 maybe translated in some embodiments via the motor controller 112 (e.g.,moved during imaging of the subject 127). However, in some embodiments,the motor controller 112 may be omitted and the imaging unit 123 may bestationary (e.g., not moved during imaging of the subject 127). As oneexample, similar to the example described below with reference to FIGS.2-3, the imaging system 100 may be configured as a stationary imagingsystem including a plurality of distributed x-ray source units (e.g.,distributed x-ray source unit 104) and a plurality of detectors (e.g.,detector 103, detector 105, detector 107, etc. of detector array 147)arranged around central axis 157, with imaging of the subject 127occurring without movement (e.g., translation, rotation, etc.) of thedistributed x-ray source units or detectors.

Although the imaging system 100 is shown including the imaging unit 123and the frame 102 as separate components, in some embodiments theimaging unit 123 and frame 102 may be a single, unitary piece. Further,in some embodiments (e.g., similar to the example described below withreference to FIGS. 2-3), the imaging unit 123 and the frame 102 may be asingle structure formed (e.g., assembled) as a result of coupling aplurality of distributed x-ray source units (e.g., the distributed x-raysource unit 104) with a plurality of detector arrays (e.g., the detectorarray 147). For example, the distributed x-ray source units and/ordetector arrays may include brackets or other fastening componentsconfigured to couple the distributed x-ray source units together withthe detector arrays, with coupled distributed x-ray source units anddetector arrays forming a rigid and self-supporting structure which maybe referred to the frame and/or imaging unit of the imaging system.Further, the coupling of the distributed x-ray source units and detectorarrays may be releasable such that the distributed x-ray source unitsand detector arrays may be decoupled from each other to disassemble theimaging system (e.g., disassemble the self-supporting structure formedby the distributed x-ray source units and detector arrays). The exampleof the distributed x-ray source units and detector arrays configured tocouple to each other to form the self-supporting structure may bereferred to herein as a modular configuration, where each modulecomprises either a single distributed x-ray source unit or a singledetector array.

The various methods and processes (such as the methods described belowwith reference to FIGS. 51-55) described further herein may be stored asexecutable instructions in non-transitory memory on a computing device(or controller) in imaging system 100, such as the computing device 116.In one embodiment, the image reconstructor 130 may include suchexecutable instructions in non-transitory memory, and may apply themethods described herein to reconstruct an image from scanning data. Inanother embodiment, the computing device 116 may include theinstructions in non-transitory memory, and may apply the methodsdescribed herein, at least in part, to a reconstructed image afterreceiving the reconstructed image from the image reconstructor 130. Inyet another embodiment, the methods and processes described herein maybe distributed across the image reconstructor 130 and the computingdevice 116.

In one embodiment, the display device 132 allows the operator toevaluate the imaged anatomy. The display device 132 may also allow theoperator to select a volume of interest (VOI) and/or request patientinformation, for example, via a graphical user interface (GUI) for asubsequent scan or processing. In some examples, the display device 132may be a monitor or touchscreen. In other examples, the display device132 may be a headset. For example, the display device 132 may be aheadset configured with a virtual reality display and/or augmentedreality display and may be configured to display images of the imagedsubject 127 acquired by the imaging system 100 layered onto a real-timeanatomical view of the subject 127 (e.g., the headset may display a viewof the subject 127 in real time, with images acquired by the imagingsystem 100 arranged virtually on top of, or adjacent to, the real-timeview of the subject 127).

Thus, imaging system 100 provides an example of a stationary CT systemthat may eliminate or reduce the number of moving parts relative totradition CT systems with rotating gantries. Such stationary CT systemsmay be lightweight and, at least in some configurations, portable and/ormodular. The stationary CT system may enable deployment of the CT systemin environments that traditionally could not support a CT imagingsystem, such as field hospitals. For example, forward deployed militaryfield hospitals (e.g., Role-2 and Role-3 military treatment facilities)typically have access to two-dimensional (2D) x-ray radiographycapabilities, which are helpful in identifying injuries. However,radiographs offer limited low contrast detectability and can only detectlarge attenuation contrasts, with limited or no visibility of bleeds,lacerations, or ruptures. Moreover, the projection nature of radiographsmakes it difficult for precise localization, geometric interpretationand quantitation of injuries.

CT imaging systems or scanners would be the imaging modality of choiceto image almost all battlefield indications, since they quickly andnon-invasively provide detailed three-dimensional (3D) images of bone,soft tissues, and foreign bodies. The 3D imaging capability offers allpossible information, from which advanced artificial intelligence (AI)algorithms can extract a wealth of information. However, conventional CTscanners have been found to be impractical to deploy with fieldhospitals because they are large, heavy, difficult to transport andinstall, and lack robustness for a battlefield environment. Even thesmallest whole-body CT scanners available today weigh several hundredsof pounds and include a high-precision rotating gantry. This makes theirtransportation, installation, and maintenance impractical in forwardlydeployed field environments where mobility and ease-of-use are desired.Furthermore, the power that is used to operate a conventional CT scanneruses a dedicated generator to supply at least 150 kVA of peak power.

There is a clinical opportunity to quickly deploy CT scanners in ruggedenvironments, such as near battle fronts, coupled with autonomousoperation and diagnosis. Today, these environments are limited to 2Dx-ray radiography systems since 3D CT imaging systems or scanners aretoo complex, hard to transport, and not robust.

There is a desire for fast assessment of casualties where immediatepatient care is performed, as in forward military deployment for combatcasualty care or field hospitals for public health emergencies. In thescenario of combat casualty care, when a wounded soldier is brought in,surgeons may benefit from immediate and actionable information on thestate of the casualties so they can expeditiously stabilize the patient.This includes detection and visualization of the most commoncombat-related indications, such as foreign objects (e.g., bullets,shrapnel, metal components in body, etc.), bone fractures, bleeds,lacerations, ruptures, and traumatic brain injuries.

For practical reasons, it is desired for this to be performed with adevice that is easy to transport and install and that works reliably androbustly in a rugged environment. Access to this capability closer tothe point of injury may significantly reduce deaths fromdifficult-to-detect internal injuries. Earliest access to this data willhelp surgeons to take immediate and decisive action, increasing survivalchances of wounded soldiers. It would therefore be desirable to providea transportable, robust, and autonomous stationary CT imaging systemthat addresses the above issues.

Embodiments of the present disclosure will now be described, by way ofexample, with reference to the drawings, in which a highly mobile (e.g.,portable), transportable, autonomous, stationary (e.g., a static,stationary or non-rotational gantry) CT imaging system or scannerwithout moving components provides CT imaging to environments that maybe inaccessible to other CT imaging systems. The CT imaging system(which may be referred to herein as a scanner and/or portable stationaryCT system) is able to provide imaging for forwardly deployed fieldhospitals, in some examples. The highly mobile, transportable,autonomous, stationary CT imaging system may provide faster assessmentof casualties during conditions in which prompt patient care is desired,as in forward military deployment for combat care or field hospitals forpublic health emergencies.

According to at least one embodiment of the present disclosure, astationary computed tomography (CT) imaging system (e.g., a static,stationary, non-rotational imaging system) may be separated intoportable components (e.g., modules) and easily assembled in the field.The CT imaging system includes a plurality of x-ray sources and aplurality of x-ray detectors arranged around a portable patient supportstructure. The CT imaging system may be operated from a portablepersonal computer, such as a laptop, iPad, tablet, smart phone, etc. Theportable personal computer may have system software and algorithmsloaded thereon that may be used for operating the CT imaging systemand/or processing data. In another example, the algorithms may bedeployed on a cloud computing network and computations may be performedin the cloud computing network (e.g., while internet access is availablewhen operating the CT imaging system). Advanced deep learning techniquesmay be used for image reconstruction (e.g., for sparse view and lowpower/low dose applications) and for image analysis, including detectingforeign objects, such as bullets, shrapnel, metal components in body,diagnosing injuries, and visualization. Visualization may be implementedthrough augmented reality and/or virtual reality media technologies. TheCT imaging system design may be self-shielded to reduce and/or eliminatenon-imaging radiation exposure even without a lead room. The CT imagingsystem may be battery powered such that it may operate withouthigh-voltage power infrastructure.

Input electrical power and radiation shielding may be configured suchthat the stationary CT imaging system may operate without a lead room ora dedicated high-voltage power infrastructure as described above. Anoverall power reduction may realized from the elimination of theelectric motor and driver that is typically provided for rotation of thex-ray source and detector gantry in a conventional CT imaging system.This overall reduction in power may result in a lower power requirementof the CT imaging systems of the present disclosure.

In an example, a transportable and autonomous stationary CT imagingsystem comprises a plurality of linear distributed x-ray sourcesinterspersed with a plurality of digital flat-panel x-ray detectors. Inone example, the stationary CT imaging system includes a plurality ofalternating compact linear distributed x-ray sources and digitalflat-panel x-ray detectors configured in a self-supporting structure(which may be referred to herein as a self-supporting stationary gantry)that includes alternating x-ray sources and x-ray detectors coupled toeach other in an arrangement that completely surrounds a portablepatient support structure through 360 degrees to form a self-supportingring-shaped imager. Each x-ray source is positioned in-between andadjacent to two x-ray detectors, and each x-ray detector positionedin-between and adjacent to two x-ray sources. The stationary CT imagingsystem includes x-ray source and x-ray detector pairs. Each x-ray sourceis positioned opposite an x-ray detector. In another example, theself-supporting stationary gantry may comprise a half-ring of x-raysources and a half-ring of x-ray detectors.

In the example stationary CT imaging system, three compact lineardistributed x-ray sources and three digital flat-panel x-ray detectorpairs are arranged in a hexagonal frame. More x-ray source and x-raydetector pairs may be used and the image reconstruction algorithm may bemodified accordingly to accommodate a different number of x-ray sourceand x-ray detector pairs and the relative angles between the x-raysource and x-ray detector pairs.

The self-supporting stationary gantry may be coupled to a portablepatient support structure (which may be referred to herein as a supportsurface). The portable patient support structure may include a patientsupport, such as a bed, gurney, stretcher, cradle, table, etc. tosupport a patent being imaged, two (or more) wheels coupled to a firstend of portable patient support structure, and two (or more) collapsiblelegs coupled to a second end of the portable patent support structure.The two collapsible legs may extend down from the portable patentsupport structure to support the patent support off of the ground in aparallel arrangement to the ground. The patient support may include two(or more) handles extending from at least one end of the patient supportto allow for easy transportability of the stationary CT imaging system.The at least two wheels may be coupled to an axle extending through acenter of the wheels or alternatively, each wheel may be attached to afork or frame member allowing the wheels to rotate when the stationaryCT imaging system is moved or transported.

The self-supporting stationary gantry, including the plurality of x-raysources and the plurality of x-ray detectors, and the portable patientsupport structure, including the patient support, two wheels, and twocollapsible legs, are all individual, lightweight removable componentsthat may be collapsible or removable and easily transportable. As thex-ray source and detector pairs are arranged around the patient support,operation of the stationary CT imaging system begins by energizing thex-ray sources in sequence or simultaneously. This provides the virtualrotation of an x-ray source to generate a sinogram of projection x-raydata. The sinogram may be reconstructed using conventional filtered backprojection, accounting for the different x-ray output of the x-raydetectors, and x-ray detector sensitivity from a calibration scan. Inthis manner, no gantry rotation is used to generate a sinogram ofprojection x-ray data for each rotation angle. In an example,self-supporting stationary gantry may include a lead-shielded gantry andradiation shields covering the front and back of the gantry bore. Inanother embodiment, artificial intelligence based autonomous operationor one-button operation of the stationary CT imaging system may beprovided.

In the example, the three x-ray sources (e.g., distributed x-ray sourceunits) and three x-ray detectors (e.g., detector arrays) weighapproximately 50 kg each and are easily assembled into theself-supporting stationary gantry forming a ring-shaped imager. Theself-supporting stationary gantry is mounted around the patient supportstructure. The location of the patient support relative to theself-supporting stationary gantry may be adjustable. In one example, anindicator member with marked gradations that may be read by a bar codereader may detect the speed that the patient support is advanced intothe stationary gantry to cover the anatomical region to be scanned. Thisinformation may by input into the image reconstruction engine to enablewhole body coverage.

In the example, each of the linear distributed x-ray sources (e.g.,distributed x-ray source units) includes at least ten separate identicalelectron guns or electron emitters (e.g., cathodes) that may be poweredat different voltage potentials to generate electrons and accelerate theelectrons in the form of an electron beam toward at least ten separateidentical stationary targets (e.g., anodes) at a ground potential togenerate x-rays. Each linear distributed x-ray source is sealed in avacuum enclosure and may have no moving components, no electric motorsfor target rotation, and no bearings. In some examples, no activepumping is performed. Instead, passive pumping via a getter componentmay be performed to ensure robustness, reduced weight, compactness, andsimplicity for battlefield deployment. The getter component may ensureappropriate pressure in the vacuum enclosure. Each electron emitterincludes electron emitter heating circuitry and electrostatic based beamoptics optimization circuitry. In an example, a high voltage generatormay be coupled to the plurality of linear distributed x-ray sources toprovide heating power to the electron emitters, accelerate electrons inan electron beam to more than 100 kV, and provide bias voltages tocontrol the x-ray focal spot size.

In the example, the electron emitters may be dispenser cathodes orcold-cathode electron emitters. In another example, smart electron beamfocusing may be available via voltage bias to tailor the x-ray focalspot size for different applications as needed. A matrix type controlmay be used for electron emitter heating circuitry and electrostaticbased beam optics optimization circuitry. In another example, oneelectron emitter may be powered at a time or multiple electron emittersmay be powered at a time, as needed. In another example, high voltagearc protection may be provided for the electronics. In another example,ion back bombarding protection may be provided for the electronemitters. In another example, electron emitter life tracking may beprovided. In another example, a potential topology of multiple targetsfor the same electron beam may be enabled via electrostatic beamdeflection. In another embodiment, artificial intelligence basedautonomous operation of the x-ray sources may be provided to optimizeoperation of the stationary CT imaging system on the fly.

The plurality of linear distributed x-ray sources may utilize a modularapproach as a multi-source CT imaging system. In this example, theplurality of linear distributed x-ray sources may include an array of 32separate electron guns, configured in a modular fashion with 32 x-rayfocal spots within a vacuum chamber. Also, in this example, 32 separatestationary targets may be used, with no moving components, no bearings,and no electric motors. By rapidly switching between these 32 separatex-ray sources, multiple views may be acquired to replace the mechanicalrotation of a CT scanner gantry. Individual emitter current control andfocal spot control may be used to control each of the 32 separateelectron guns. For example, compact and robust electronics may be usedto adjust focusing parameters, emitted current per focal spot, durationof x-ray exposures. Innovative beam optics may be provided for increasedimage resolution tailored for different applications.

Tomographic image reconstruction techniques employed on the stationaryCT imaging system may include model-based iterative reconstruction forlow dose/low power applications, and wide-cone reconstruction for alarge-area detector. This disclosure also contemplates the use of deeplearning techniques for sparse view and low dose image reconstruction toproduce diagnostic quality images from a reduced number of views. Deeplearning based image reconstruction provides a computationally efficientway to produce high-quality images from sparse, low power data on aportable personal computer. A CT scan is automatically analyzed andannotated in terms of detection and visualization of the most commoncombat-related indications, such as foreign objects (e.g., bullets,shrapnel, metal components in body, etc.), bone fractures, bleeds,lacerations, ruptures, and traumatic brain injuries. Image analytics andannotated images may be visualized by a healthcare professional throughoverhead displays or through virtual reality technology.

This stationary CT imaging system may be used for military applicationsin some examples. As another example, this stationary CT imaging systemmay be useful in the case of pandemics where quick access to 3D imaging(in the form of low-end CT) is desired.

Referring to FIG. 2, a perspective view of an imaging system 200 similarto, or the same as, the example described above is shown. Imaging system200 may be referred to herein as a modular imaging system, stationary CTimaging system, and/or portable imaging system. Imaging system 200 is anon-limiting example of imaging system 100 and thus may include severalcomponents similar to those described above with reference to FIG. 1.For example, imaging system 200 includes a plurality of distributedx-ray source units (e.g., a first distributed x-ray source unit 202, asecond distributed x-ray source unit 204, and a third distributed x-raysource unit 206), which may each be similar to the distributed x-raysource unit 104 described above with reference to FIG. 1. Thedistributed x-ray source units are releasably coupled to (e.g., fixedlycoupled to, and able to be decoupled from) a plurality of detectorarrays that are similar to the detector array 147 shown by FIG. 1 anddescribed above. In the example shown in FIG. 2, the plurality ofdetector arrays includes a first detector array 208, a second detectorarray 210, and a third detector array 212. The plurality of distributedx-ray source units and the plurality of detector arrays form aself-supporting structure 201 including a central opening 203 shaped toreceive a subject 216 to be imaged. The subject 216 may be positionedalong a central axis 226 of the central opening 203 for imaging via theimaging system 200. For example, the subject 216 (e.g., a patient) maybe supported by a support surface 214, and the subject 216 and thesupport surface 214 may each be moved along the central axis 226 intothe central opening 203. The support surface 214 may be joined to legs(e.g., a leg 222, a leg 224, etc.), wheels (e.g., a wheel 218, a wheel220, etc.), etc. configured to maintain the vertical position of thesupport surface 214 relative to the central opening 203. Stationaryimaging (or imaging via a stationary imaging system) may refer toimaging of the subject without rotation of components of the imagingsystem 200 around the subject (e.g., without rotation of the distributedx-ray source units). In the example shown by FIGS. 2-3, the imagingsystem 200 is configured to perform stationary imaging and isadditionally configured to be portable (e.g., via decoupling of thedistributed x-ray source units and the detector arrays) such that theimaging system 200 may be more easily moved from one location toanother.

The self-supporting structure 201 may be referred to herein as a frameor imaging unit of the imaging system 200 (e.g., similar to the frame102 and/or the imaging unit 123 described above with reference to FIG.1). The self-supporting structure 201 is a rigid assembly resulting fromthe coupling of the plurality of distributed x-ray source units with theplurality of detector arrays. In some examples, the plurality ofdistributed x-ray source units may couple in interlocking engagementwith the plurality of detector arrays to form the self-supportingstructure 201. In other examples, fasteners such as brackets mayreleaseably couple the plurality of distributed x-ray source units withthe plurality of detector arrays. The distributed x-ray source units andthe detector arrays are coupled together such that the central axis 226of the central opening 203 of the self-supporting structure 201 isarranged approximately parallel with a ground surface 205 on which theimaging system 200 sits. In some examples, a balance (e.g., weightdistribution) of the self-supporting structure 201 may be configuredsuch that the self-supporting structure 201 may be maintained in anupright position (e.g., with the central axis 226 arranged approximatelyparallel with the ground surface 205, as shown by FIGS. 2-3) withoutadditional supports (e.g., without components other than the distributedx-ray source units, detector arrays, or brackets). For example, thefirst distributed x-ray source unit 202, the second distributed x-raysource unit 204, the third distributed x-ray source unit 206, the seconddetector array 210, and the third detector array 212 may each besupported by the first detector array 208 in the vertical directionrelative to the ground surface 205 on which the imaging system 200 sits.

In other examples, the self-supporting structure 201 may include one ormore rods or other components configured to maintain the self-supportingstructure 201 in the upright position, with the relative position of theindividual distributed x-ray source units and the detector arrays beingmaintained via the coupling between the distributed x-ray source unitsand the detector arrays (e.g., the interlocking engagement of thedistributed x-ray source units with the detector arrays and/or thebrackets coupling the distributed x-ray source units with the detectorarrays).

Each distributed x-ray source unit may be interchangeable with eachother distributed x-ray source unit of the plurality of distributedx-ray source units forming the self-supporting structure 201. Forexample, the imaging system 200 may include the first distributed x-raysource unit 202, the second distributed x-ray source unit 204, the thirddistributed x-ray source unit 206, the first detector array 208, thesecond detector array 210, and the third detector array 212, as shown byFIGS. 2-3. During assembly of the distributed x-ray source units withthe detector arrays in order to form the self-supporting structure 201,the distributed x-ray source units may be interchanged with each otherwithout affecting an imaging quality of the imaging system 200. Forexample, the first distributed x-ray source unit 202 and the seconddistributed x-ray source unit 204 may be interchanged (e.g., the firstdistributed x-ray source unit 202 may instead be arranged at thelocation of the second distributed x-ray source unit 204 shown by FIGS.2-3, and the second distributed x-ray source unit 204 may instead bearranged at the location of the first distributed x-ray source unit 202shown by FIGS. 2-3) without altering the imaging quality of the imagingsystem 200 (e.g., without increasing an imaging noise, x-ray radiationscattering, etc. of the imaging system 200). Similarly, the detectorsarrays may be interchanged with each other without affecting the imagingquality. For example, the second detector array 210 may be interchangedwith the third detector array 212 without altering the imaging quality(e.g., the second detector array 210 may instead be arranged at thelocation of the third detector array 212 shown by FIGS. 2-3, and thethird detector array 212 may instead be arranged at the location of thesecond detector array 210 shown by FIGS. 2-3). During conditions inwhich the distributed x-ray source units and the detector arrays arecoupled together to form the self-supporting structure 201 describedabove, the first distributed x-ray source unit 202, the seconddistributed x-ray source unit 204, the third distributed x-ray sourceunit 206, the first detector array 208, the second detector array 210,and the third detector array 212 are each vertically fixed (e.g.,maintained in position in the vertical direction) within a same imagingplane 230 relative to the ground surface 205 on which the imaging system200 sits.

The interchangeable characteristic of the distributed x-ray source unitsand the detector arrays may be increased in some examples by configuringeach of the distributed x-ray source units to have a same shape (e.g.,an equal sizing) and configuring each of the detector arrays to have asame shape. For example, the first distributed x-ray source unit 202 mayhave a length 364 along a centerline of the first distributed x-raysource unit 202, the second distributed x-ray source unit 204 may have alength 368 along a centerline of the second distributed x-ray sourceunit 204, and the third distributed x-ray source unit 206 may have alength 372 along a centerline of the third distributed x-ray source unit206. The length 364, the length 368, and the length 372 may each beequal (e.g., a same amount of length). Similarly, the first detectorarray 208 may have a length 370 along a centerline of the first detectorarray 208, the second detector array 210 may have a length 374 along acenterline of the second detector array 210, and the third detectorarray 212 may have a length 366 along a centerline of the third detectorarray 212, with the length 370, the length 374, and the length 366 beingequal (e.g., a same amount of length). In some examples, the length 364,the length 368, the length 372, the length 370, the length 374, and thelength 366 may each be equal. By configuring the distributed x-raysource units and detector arrays to have the same size, an ease ofassembling the distributed x-ray source units and detector arrays toform the self-supporting structure 201 may be increased. For example, auser may couple the detector arrays with the distributed x-ray sourceunits in an alternating arrangement (e.g., with each distributed x-raysource unit coupled between two adjacent detector arrays) to assemblethe self-supporting structure 201 without maintaining the exactsequential order of the distributed x-ray source units in the clockwisedirection or counterclockwise direction between each assembly anddisassembly operation. For example, in one assembled configuration, thefirst distributed x-ray source unit 202 may be arranged at the top ofthe imaging system 200, between the second detector array 210 and thirddetector array 212, as shown by FIGS. 2-3, while in another assembledconfiguration, the second distributed x-ray source unit 204 may insteadbe arranged at the top of the imaging system 200, between the seconddetector array 210 and third detector array 212, and the firstdistributed x-ray source unit 202 may instead be arranged verticallybelow the second detector array 210, between the third detector array212 and the first detector array 208, without altering the imagingquality of the imaging system 200.

In the example shown by FIGS. 2-3, the self-supporting structure 201formed by the coupling of the distributed x-ray source units with thedetector arrays has a hexagonal profile. In particular, as shown by FIG.3, the first distributed x-ray source unit 202 is arranged at a firstside 340 of the hexagonal profile, the first detector array 208 isarranged at a second side of the hexagonal profile opposite to the firstside 340 (e.g., across the central axis 266 relative to the first side340), the second distributed x-ray source unit 204 is arranged at athird side 344 of the hexagonal profile, the second detector array 210is arranged at a fourth side 346 of the hexagonal profile opposite tothe third side 344 (e.g., across the central axis 266 relative to thethird side 344), the third distributed x-ray source unit 206 is arrangedat a fifth side 348 of the hexagonal profile, and the third detectorarray 212 is arranged at a sixth side 350 of the hexagonal profileopposite to the fifth side 348 (e.g., across the central axis 266relative to the fifth side 348).

Each of the distributed x-ray source units and the detector arrays maybe spaced approximately equally apart from the central axis 226. Forexample, as shown by FIG. 3, the first distributed x-ray source unit 202is spaced apart from the central axis 226 by the length 352, the firstdetector array 208 is spaced apart from the central axis 226 by thelength 358, the second distributed x-ray source unit 204 is spaced apartfrom the central axis 226 by the length 356, the second detector array210 is spaced apart from the central axis 226 by length 362, the thirddistributed x-ray source unit 206 is spaced apart from the central axis226 by the length 360, and the third detector array 212 is spaced apartfrom the central axis 226 by length 354. Each of the length 352, thelength 354, the length 356, the length 358, the length 360, and thelength 362 are arranged around the central axis 226 (e.g., the lengthsextend radially from the central axis 226) and may be an equal amount oflength (e.g., the length 352 may be a same amount of length as thelength 358). Further, a first axis 314 extending along the centerline ofthe first distributed x-ray source unit 202 is parallel with a secondaxis 306 extending along the centerline of the first detector array 208,a third axis 304 extending along the centerline of the seconddistributed x-ray source unit 204 is parallel with a fourth axis 310extending along the centerline of the second detector array 210, and afifth axis 308 extending along the centerline of the third distributedx-ray source unit 206 is parallel with a sixth axis 302 extending alongthe centerline of the third detector array 212. The first axis 314 isarranged at a first angle 380 relative to the fourth axis 310 and asecond angle 382 relative to the sixth axis 302, the third axis 304 isarranged at a third angle 384 relative to the sixth axis 302 and afourth angle 386 relative to the second axis 306, and the fifth axis 308is arranged at a fifth angle 388 relative to the second axis 306 and asixth angle 390 relative to the fourth axis 310. In this configuration,the first detector array 208 couples to the second distributed x-raysource unit 204 at the fourth angle 386 and couples to the thirddistributed x-ray source unit 206 at the fifth angle 388, the seconddetector array 210 couples to first distributed x-ray source unit 202 atthe first angle 380 and couples to the third distributed x-ray sourceunit 206 at the sixth angle 390, and the third detector array 212couples to the first distributed x-ray source unit 202 at the secondangle 382 and couples to the second distributed x-ray source unit 204 atthe third angle 384. In some examples, the first angle 380, the secondangle 382, the third angle 384, the fourth angle 386, the fifth angle388, and the sixth angle 390 may be equal (e.g., the same amount ofangle or number of degrees). The first detector array 208 is arranged atan angle 392 relative to the second detector array 210, and the firstdetector array 208 is arranged at an angle 394 relative to the thirddetector array 212. In some examples, the angle 392 and the angle 394may be equal (e.g., the same amount of angle or number of degrees). Insome examples, the angle 392 and the angle 394 may each be 60 degrees.

The distributed x-ray source units and the detector arrays are coupledtogether such that each of the distributed x-ray source units isarranged between two adjacent detector arrays. For example, the firstdistributed x-ray source unit 202 is arranged between the seconddetector array 210 and the third detector array 212, the seconddistributed x-ray source unit 204 is arranged between the third detectorarray 212 and the first detector array 208, and the third distributedx-ray source unit 206 is arranged between the first detector array 208and the second detector array 210. In this configuration, thedistributed x-ray source units alternate with the detector arrays in aclockwise or counterclockwise direction around the central axis 226. Forexample, in the clockwise direction, the first distributed x-ray sourceunit 202 couples to the third detector array 212, the third detectorarray 212 couples to the second distributed x-ray source unit 204, thesecond distributed x-ray source unit 204 couples to the first detectorarray 208, the first detector array 208 couples to the third distributedx-ray source unit 206, the third distributed x-ray source unit 206couples to the second detector array 210, and the second detector array210 couples to the first distributed x-ray source unit 202.

In some examples, the detector arrays and distributed x-ray source unitsmay be configured to interlock directly with each other (e.g., features,such as teeth, projections, etc. formed on each distributed x-ray sourceunit may be configured to interlock with counterpart features, such asrecesses, depressions, etc. formed on adjacent detector arrays). Inother examples, such as the example shown by FIGS. 2-3, the distributedx-ray source units and the detector arrays may be configured to coupletogether via brackets. In particular, in the example shown, the firstdistributed x-ray source unit 202 couples to the third detector array212 via a bracket 318 including an arm 316 and further couples to thesecond detector array 210 via a bracket 338 including an arm 336. Thesecond distributed x-ray source unit 204 couples to the third detectorarray 212 via a bracket 322 including an arm 320 and further couples tothe first detector array 208 via a bracket 326 including an arm 324. Thethird distributed x-ray source unit 206 couples to the first detectorarray 208 via a bracket 328 including an arm 330 and further couples tothe second detector array 210 via a bracket 332 including an arm 334. Insome examples, the brackets and/or arms may be formed integrally withthe distributed x-ray source units and/or detector arrays. For example,the bracket 318 and the arm 316 may be formed together with thedistributed x-ray source unit 202 as a single, unitary piece. In otherexamples, the brackets and/or arms may be separate components that arecoupled to the distributed x-ray source units and/or detector arrays inorder to fixedly couple the distributed x-ray source units with thedetector arrays to form the self-supporting structure 201. The bracketsmay be configured to releaseably couple the distributed x-ray sourceunits with the detector arrays such that the distributed x-ray sourceunits and detector arrays remain coupled together for imaging of thesubject 216 (shown by FIG. 2) and may be decoupled from each other fortransporting the imaging system 200 from one location to another, formaintenance, etc. For example, the brackets may include one or morelocking features (e.g., latches, etc.) configured to maintain thebrackets in engagement with the distributed x-ray source units anddetector arrays, and to unlock (e.g., decouple) the distributed x-raysource units from the detector arrays responsive to an unlocking of thelocking features (e.g., actuation of a button, lever, etc. of thelocking features of each bracket). By configuring the distributed x-raysource units and the detector arrays to decouple from each other whendesired (e.g., via unlocking of the locking features of the bracketsand/or disengagement of interlocking features of the distributed x-raysource units and detector arrays during disassembly of the imagingsystem 200 following an imaging of the subject 216), a portability ofthe imaging system 200 may be increased. The imaging system 200 may thusbe assembled for imaging of subjects (e.g., the subject 216) inlocations that may be difficult to accommodate larger imaging systemsand/or less portable imaging systems.

Configuring the imaging system 200 to include an odd number ofdistributed x-ray source units (e.g., three) and an odd number ofdetector arrays (e.g., three) may increase an imaging quality of theimaging system 200 relative to configurations that include an evennumber of detector arrays and/or distributed x-ray source units.Further, by configuring the imaging system 200 to include exactly threedistributed x-ray source units and exactly three detector arrays coupledtogether to form the self-supporting structure 201 with the hexagonalprofile as described above may increase a stability, imaging quality,and/or ease of assembly of the imaging system 200. For example, thehexagonal profile provided by the configuration including exactly threedistributed x-ray source units and exactly three detector units mayincrease a balance of the imaging system 200 and reduce a complexity ofassembly of the imaging system 200. Further, the exactly threedistributed x-ray source units and the exactly three detector units mayprovide for a complete scan of the subject 216 (e.g., 360 degrees ofimaging of the subject 216) during conditions in which the subject 216is imaged by the imaging system 200 and the image of the subject 216 isreconstructed according to the methods described herein.

In an example operation of the imaging system 200, the imaging systemmay image the subject 216 (e.g., acquire a scan of the subject 216) byenergizing the first distributed x-ray source unit 202 to emit x-rayradiation in the vertical direction (e.g., toward the first detectorarray 208 arranged toward the ground surface 205), and the x-rayradiation emitted by the first distributed x-ray source unit 202 may beintercepted by the first detector array 208. Imaging the subject 216 mayfurther include energizing the second distributed x-ray source unit 204to emit x-ray radiation toward the second detector array 210 (e.g., inthe direction of the length 356 and the length 362), and the x-rayradiation emitted by the second distributed x-ray source unit 204 may beintercepted by the second detector array 210. Imaging the subject 216may further include energizing the third distributed x-ray source unit206 to emit x-ray radiation toward the third detector array 212 (e.g.,in the direction of length 360 and length 354), and the x-ray radiationemitted by the third distributed x-ray source unit 206 may beintercepted by the third detector array 212. Energizing the distributedx-ray source units may include providing electrical energy to thedistributed x-ray source units via a portable energy source (e.g., aportable battery unit, similar to x-ray power source 145 described abovewith reference to FIG. 1). Throughout the imaging of the subject 216,the imaging system 200 is maintained in a stationary (e.g., non-moving)position. In particular, as the subject 216 is imaged, the distributedx-ray source units and the detector arrays are not moved (e.g., rotated,translated, etc.). In order to provide a full view of the subject 216being imaged, the imaging system 200 may reconstruct the image of thesubject 216 according to the methods described herein (e.g., via a deeplearning network).

Referring to FIGS. 4-5, another imaging system 400 is shown. The imagingsystem 400 may be referred to herein as an upright imaging system,stationary CT system, and/or stationary CT scanner. The imaging system400 may provide quick, automated, low-dose, low-cost chest CT scanningof a subject, in some examples. The imaging system 400 may includeseveral components similar to those described above with reference toFIG. 1. For example, the imaging system 400 includes a distributed x-raysource unit 417. The distributed x-ray source unit 417 includes aplurality of x-ray emitters, similar to the emitters described abovewith reference to FIG. 1 (e.g., emitter 106, emitter 108, emitter 109,etc.). The imaging system 400 further includes a detector array 416. Thedetector array 416 includes a plurality of x-ray detectors, similar tothe detectors described above with reference to FIG. 1 (e.g., detector103, detector 105, detector 107, etc.). Because the multiple emitters ofthe distributed x-ray source unit 417 may emit x-ray radiation (e.g.,x-ray beams) spanning an angular range around a central axis 406 of theimaging system 400, the imaging system 400 may image a subject (e.g.,the subject 216 shown by FIG. 2) without rotation of the distributedx-ray source unit 417 and the detector array 416 around the central axis406. For example, the emitters of the distributed x-ray source unit 417may be arranged over an angular range of 360 degrees surrounding thesubject. As another example, the emitters may be arranged over anangular range of 180 degrees surrounding the subject. Similarly, thedetectors of the detector array 416 may extend over an angular range of360 degrees, 180 degrees, etc. around the subject. The imaging system400 may utilize the image reconstruction approaches described herein inorder to provide a full image of the subject with sparse-view datasetsand/or limited view angle datasets.

In some examples, the imaging system 400 may be configured as asemi-stationary imaging system in which the detector array 416 isrotatable around the subject but the distributed x-ray source unit 417is maintained in a fixed position around the subject (e.g., thedistributed x-ray source unit 417 is not rotated around the subject).The imaging system 400 may be configured such that the distributed x-raysource unit 417 and the detector array 416 may be translated vertically(e.g., moved up and down a vertical length of the imaging system 400)during imaging of the subject (e.g., in order to scan various portionsof the chest of the subject, to perform a helical scan, etc.). In someexamples, the imaging system 400 may translate the subject verticallyrelative to the distributed x-ray source unit 417 and the detector array416 during imaging of the subject.

Because the imaging system 400 does not include a rotating gantry, acost of the imaging system 400 may be reduced relative to conventionalimaging systems that include a gantry configured to rotate around thesubject to be imaged. Further, because the subject is imaged by theimaging system 400 while in an upright position, a size of the imagingsystem 400 may be reduced relative to imaging systems that areconfigured to image the subject in a prone position. Because the subjectis maintained in the upright position during imaging, a flattening ofthe subject as a result of gravity may be reduced, which may enable thescan field of view, chamber size, and radiation dosage of the imagingsystem 400 to be reduced. As one example, the scan field of view may bereduced to a 30 centimeter diameter, compared to a 50 centimeterdiameter often used by conventional imaging systems. If truncation ofthe imaging of the subject occurs, a truncation correction may be usedaccording to the methods described herein. For example, a deep learningalgorithm (e.g., a generative adversarial network) may be trained toestimate the truncated data. Training data for the deep-learningalgorithm may be obtained by utilizing untruncated CT datasets as thelabel and truncated CT datasets as the input. In some examples,iterative reconstruction may be used. In some examples the view samplingof the subject may be non-uniform. For example, the view sampling may belocally dense, but sparse overall (e.g., with 4 detectors followed by agap, in a repeating pattern arrangement). The spacing of the emitterswithin the distributed x-ray source unit 417 and/or the spacing of thedetectors within the detector array 416 may be selected to increase aview sampling. For example, opposite views may be interlaced to reduce aredundancy in conjugate rays. In some examples, an odd number of x-rayemitters may be arranged uniformly within the distributed x-ray sourceunit to provide 360 degrees of imaging of the subject. As one example,the x-ray emitters may be arranged at positions corresponding to 0□ and8□ relative to a given origin (e.g., an opening 419 of the imagingsystem 400 shaped to receive the subject to be imaged) and on theopposite side a focal spot may be positioned at −4°+180°, 4°+180°, and12°+180°. As another example, segments of the x-ray emitters may betilted to be parallel with the central axis 406 or to be at anotherangle to the central axis 406 (e.g., in an oblique arrangement. In someexamples, a position of an electron beam directed toward the anode ofeach x-ray emitter (e.g., from a corresponding cathode of the emitter)may be adjusted to sweep along the anode.

In some examples, the available view range provided by the arrangementof the emitters within the distributed x-ray source unit and thedetectors within the detector array may be less than 180 degrees plusthe fan angle. For example, the view range may be angular range of thex-ray radiation emitted by the distributed x-ray source unit may be 160degrees while the angular range at which the detector array mayintercept x-ray radiation may be 200 degrees. In such examples, deeplearning may be used according to the methods described herein toextrapolate additional views in the view angle direction. If the finalreconstructed image volumes have better spatial resolution in onedirection (e.g. in coronal planes) compared to another direction (e.g.in the sagittal planes), the data sets may be primarily shown as coronalimages.

It is often desirable to perform a scan of the subject quickly in orderto reduce a likelihood of artifacts resulting from motion of the subject(e.g., respiratory and/or cardiac motion). However, in configurationsthat have a lower amount of electrical power available at the emitters,scan time may be increased. In order to reduce artifacts resulting fromthe motion of the subject while performing longer scans, time-sequentialsampling may be utilized according to the methods described herein.

The imaging system 400 includes a chamber 421 shaped to enclose thesubject to be imaged. The subject may be supported in the uprightposition within the chamber 421 via support surface 408 (which may bereferred to herein as a subject support surface). The support surface408 may be a pedestal, as one example. In some examples, the supportsurface 408 may be motorized (e.g., coupled to a motor 433 controlled bya support surface motor controller, such as the support surface motorcontroller 126 shown by FIG. 1 and described above) such that thesupport surface 408 may move in the vertical direction (e.g., a verticaldirection 420, parallel with central axis 406) in order to adjust thevertical position of the subject within the chamber 421.

The imaging system 400 further includes an annular imaging unit 412. Theannular imaging unit 412 includes the distributed x-ray source unit 417and the detector array 416 disposed therein, with the distributed x-raysource unit 417 and detector array 416 arranged at an inner perimeter423 of the annular imaging unit 412. The distributed x-ray source unit417 may be arranged opposite to the detector array 416 across thecentral axis 406. The annular imaging unit 412 surrounds the chamber 421such that the inner perimeter 423 of the annular imaging unit 412 isarranged adjacent to the chamber 421. The annular imaging unit 412 maybe driven by a motor to translate in the vertical direction (e.g., thedirection of central axis 406) in a fixed angular orientation relativeto the chamber 421 and inner enclosure 422. In particular, the annularimaging unit 412 may be configured to move in the direction parallelwith the central axis 406 without rotating around the central axis 406(e.g., without adjusting the angular position of the annular imagingunit 412 in direction 418 around the central axis 406). In someexamples, the annular imaging unit 412 may include a shroud 414partially enclosing the annular imaging unit 412.

The imaging system 400 includes an outer enclosure 410 and the innerenclosure 422. In some examples, one or both of the outer enclosure 410and inner enclosure 422 may be formed of a material transparent and/ortranslucent to visible light (e.g., glass, polycarbonate, etc.transparent to light having a wavelength within a range of 400 to 750nanometers) such that during conditions in which the subject ispositioned within the chamber 421 for imaging, the subject may bevisible within the chamber 421 from an exterior of the chamber 421. Theouter enclosure 410, inner enclosure 422, and support surface 408 mayeach be supported by a base 402 of the imaging system 400 (e.g.,supported in direct contact with the base 402). The inner enclosure 422may be fixedly coupled to the base 402 such that the inner enclosure 422does not rotate relative to the base 402. However, the outer enclosure410 may be rotatably coupled to the base 402 such that the outerenclosure 410 may rotate relative to the base 402 and the innerenclosure 422. The inner enclosure 422 includes opening 419 and theouter enclosure includes an opening 425. During conditions in which theopening 419 and the opening 425 are aligned (e.g., arranged at a samerotational position around the central axis 406, the subject to beimaged may pass through the opening 419 and the opening 425 to enter thechamber 421. The outer enclosure 410 may then be rotated relative to theinner enclosure 422 in order to seal the opening 419 of the innerenclosure 422 via the inner surfaces of the outer enclosure 410. Alength of the opening 419 around the central axis 406 (e.g., an arcuatelength of the opening 419) may be less than or equal to a length of theopening 425 around the central axis 406 (e.g., an arcuate length of theopening 425).

The inner enclosure 422 and the outer enclosure 410 are each sealed atan end 407 of the imaging system 400 (e.g., a top end) opposite to thebase 402 by a cap 404. The cap 404 may include a plurality ofillumination elements 427 configured to emit ultraviolet radiationthrough the chamber 421 and in a direction of the support surface 408.For example, following imaging of the subject, the subject may beremoved from the chamber 421 and the chamber 421 may be disinfected viathe ultraviolet radiation emitted by the illumination elements 427. Insome examples, the base 402 may include a plurality of openings, such asopening 429, which may fluidly couple the chamber 421 to a disinfectantsource 431 (indicated schematically in FIG. 4). In some examples, thedisinfectant source 431 may be a reservoir containing a disinfectantvapor (e.g., hydrogen peroxide), and the disinfectant vapor may flowinto the chamber 421 for cleaning of the chamber 421 following imagingof the subject. In order to reduce a likelihood of spraying thedisinfectant vapor outside of the chamber 421, the outer enclosure 410may be rotated to seal the opening 419 during conditions in which acleaning operation is commanded (e.g., conditions in which thedisinfectant vapor is supplied to the chamber 421 via opening 429 and/orultraviolet radiation is emitted via illumination elements 427).

In an example operation of the imaging system 400, a scan of the subjectmay be acquired while the subject is supported in the upright positionwithin the chamber 421 by energizing the distributed x-ray source unit417 to emit x-ray radiation through the subject and across the chamber421, with the x-ray radiation being received at the detector array 416.While the subject is being imaged (e.g., scanned), the angular positionof the distributed x-ray source unit 417 is maintained relative to thechamber 421 throughout an entire duration of the imaging (e.g., thedistributed x-ray source unit 417 is not rotated around the subject). Inparticular, the angular position of the imaging unit 412 is maintainedthroughout the duration of the scan. However, the imaging unit 412 maybe driven in the vertical direction 420 via the motor 433 (shownschematically by FIG. 4) during imaging of the subject in order to imagea larger portion of the subject and/or to perform a helical scan. Themotor 433 may be controlled by a motor controller, similar to the motorcontroller 112 shown by FIG. 1 and described above. Because thedistributed x-ray source unit 417 and the detector array 416 are eachdisposed within the imaging unit 412, driving the imaging unit 412 inthe vertical direction 420 moves the distributed x-ray source unit 417and the detector array 416 in unison in the vertical direction 420. Insome examples, the subject may be moved in the vertical direction 420within the chamber 421 during imaging of the subject by driving thesupport surface 435 in the vertical direction 420 via the motor 433(indicated schematically in FIG. 4).

Referring to FIGS. 6-7, different targets (e.g., anodes) of an x-rayemitter are shown. In particular, FIG. 6 shows a side view of target600, and FIG. 7 shows a side view of target 700. The target 600 and/orthe target 700 may be included in the imaging systems described herein(e.g., the targets shown by FIGS. 6-7 may be included distributed x-raysource unit 104 shown by FIG. 1 and described above, distributed x-raysource unit 202 shown by FIG. 2 and described above, etc.). For example,anode 111, anode 115, anode 121, etc. shown by FIG. 1 and describedabove may be similar to, or the same as, target 600 and/or target 700.Conventional x-ray targets are often rotating targets (e.g., discscomprising molybdenum with a track of tungsten) or stationary targets(e.g., blocks of copper with tungsten brazed thereto). However, thetargets contemplated herein may include diamond layers and/orphase-change materials (PCMs). As one example, layers of diamond may beincluded proximate to a tungsten layer at which electrons emitted bycathode (e.g., cathode 113, cathode 117, etc. shown by FIG. 1 anddescribed above). As another example, PCMs may be included within aninterior of the targets. The diamond layers and/or PCMs may decrease arate at which the temperature of the targets increases while inoperation (e.g., while electrons are intercepted by the targets).

In the example shown by FIG. 6, the target 600 includes a region 602 ofPCM disposed within an interior of the target 600. The region 602 mayreduce a rate at which the temperature of the target 600 increases bycontrolling a bulk temperature of the target 600. The region 602 of PCMmay absorb a portion of heat provided to the target 600, where the heatis utilized to change the phase of the PCM (e.g., from solid to liquid,or vice versa) rather than to increase the temperature of the target600. The trapezoidal shape of the region 602 of PCM may increase a depthor thickness of the region 602 within the target 600, which may furtherincrease the heat absorption characteristic of the region 602 of PCM.

In the example shown by FIG. 7, the target 700 includes a diamond layer702 in addition to a region 704 of PCM. The diamond layer 702 and region704 of PCM may together further reduce a rate at which the temperatureof the target 700 increases. In particular, the diamond layer 702 mayreduce temperature increases of the target 700 at portions of the target700 proximate to an area at which electrons are intercepted by thetarget 700. Further, the diamond layer 702 may increase a transfer ofheat to the region 704 of PCM, which may reduce a heating of otherportions of the target 700. In some examples, the diamond layer 702 andregion 704 of PCM may reduce a typical operating temperature of thetarget 700 by 100-250 degrees Celsius.

The target 600 and/or the target 700 may include an alloy of copper,aluminum, and silicon, in some examples. The copper, aluminum, andsilicon may have a higher specific heat capacity in both single (2.5×)and two-phase zones (1.1×) compared to an alloy of Copper, Zinc, andPhosphorus. Trapezoidal PCM regions and the copper, aluminum, andsilicon alloy may reduce a rate of temperature increase for smalltargets in particular, while diamond layers may reduce the rate oftemperature increase for large targets in particular. In some examples,the diamond layer may be 0.5 mm thick.

Each of the target 600 shown by FIG. 6 and the target 700 shown by FIG.7 may include tracks formed from several materials. For example, target600 may include a track formed from tungsten and another track formedfrom molybdenum to generate different energy spectrum from each track.Electron beams emitted by the respective cathode may be deflected backand forth between the tracks. In some examples, the cathode may emit twoindividual electron beams, with one beam directed toward the tungstentrack and with one beam directed toward the molybdenum track. In someexamples, each track may be formed of a same material, and the twoelectron beams may be deflected between the two tracks to reduce alikelihood of degradation of the target.

Referring to FIG. 8, an electron source 800, a target 802, an electronbeam 804, a magnetic lens 806, a PIE electrode 808, a plurality of ions810, and a small beam spot 812 are schematically shown. The electronsource 800 may be a cathode similar to the anodes described above withreference to FIG. 1, and the target 802 may be an anode similar to theanodes described above with reference to FIG. 1.

In x-ray source units, it may be desirable to reduce a likelihood ofspit and/or emitter degradation. Emitters can be affected bybackstreaming ions and by high voltage spits. The voltage between thegate electrode and the field emitters may be constrained. To clamp thevoltage, an integrated thyristor structure may be utilized. Thethyristor structure may breakdown during conditions in which the voltageexceeds a threshold voltage. The structure may be integrated to controlcurrent paths and to route the spit current in desired areas away fromthe field emitters.

Further, the temperature increase may be constrained during spits. Heatmay be produced by current flowing through electrically resistivematerial, with the heat dissipating through thermal conduction andirradiation. A thick gate electrode may be provided, where the electrodeis coated with a high thermal conductivity material such as diamond.Areas of increased resistivity may be provided where it is desirable todissipate the energy into heat. The areas of increased resistivity maybe inside or outside of a vacuum structure. Emitters may have a reducedlikelihood of degradation through utilization of an increased vacuumand/or active getters that are heated. The getters may be heated whenpressure increased, and the ion collector and number of arcs may bemonitored.

A back-scatter electron collector may be included. The back-scatteredelectron collector may collect backscatter electrons and decrease thetarget temperature during operation. The back-scattered electroncollector may absorb a portion of the heat during a spit throughradiation, and may be coated with high emissivity coating. Various othercomponents may be coated with coatings having low secondary electronemission.

A likelihood of field emitter degradation may be decreased via activegetters. If a sealed vacuum chamber is desired, active getters mayincrease performance.

Assembling the targets at specific angles and adding a shroud around thetargets may be effective against ions. Ion traps toward the electron gunmay additionally reduce a likelihood of degradation. An ion trap orbarrier may be biased at one positive voltage to repel ions. Other ioncontrol systems may include several electrodes, similar to the exampleshown.

Electrons emitted by a cold cathode may be utilized as a source ofprimary electrons that hit another plate to create secondary electronemission. Such a configuration may be a booster and may provide areduced likelihood of degradation versus ions and arcs. The aboveconfigurations may be applied to distributed x-ray sources, such as thedistributed x-ray source unit 104 shown by FIG. 1 and described above.

Referring to FIGS. 9-12, various different high voltage insulatorconfigurations are shown. The high voltage insulators may be includedwithin the distributed x-ray source units described herein (e.g.,distributed x-ray source unit 104 shown by FIG. 1 and described above).One of the drivers for x-ray source size is the size of the high voltageinsulators. Conventional insulators are often cylindrical orpancake-shaped. It may be desirable to reduce a size of the insulatorsfor increased performance. In some examples, non-linear resistivematerials may be applied as coatings to the resistors. Such coatings mayinclude silicon carbide or titanium nitride. The coatings may reduce thefield concentration and smooth out the field to reduce surface flashoverand the insulator dimensions.

In some examples, machinable aluminum nitride may be used instead ofalumina to provide zig-zag shaped surface to increase the surfacetracking length and reduce the radial dimensions. For example, aluminumnitride may be machined to form the insulator 900 shown by FIG. 9, theinsulator 1000 shown by FIG. 10, and/or the insulator 1100 shown by FIG.11. A stress grading coating or low secondary emission coating may beapplied to reduce the triple conjunction field, and the length of aninsulator may be reduced by about 50% relative to conventional examples.

The triple point junction effect may be shielded by the geometric designof the electrode, with the electrode folding over the triple junctionpoint to act as a Faraday cage. If the electrical stress is too large atthe area where it is facing to the end of the electrode, a nonlinearresistive coating can be applied to lower the field further. Forexample, the inner ring diameter of the ceramic could be smaller, or theheight could be taller to reduce the outer diameter of the ceramic disc(e.g., similar to the electrode 1200 shown by FIG. 12). The higher wallmay be shaped maintain the angle at the bottom portion the same to avoida stress concentration at the bottom portion. However, stress gradingmay be applied to the bottom portion as well.

In some systems, tiled emitters may be included to provide emission fromspecific zones to provide small or large spots and wobble. Multiplex-ray sources may be connected to a same high voltage generator. Forexample, one end of a connection may connect to the generator, andanother end may be split to connect to multiple different x-ray sources.As another example, every odd x-ray source may be coupled to a firstgenerator and every even x-ray source may be coupled to a secondgenerator to provide a dual kVp. The two generators may be operated atthe same voltage for arc and spit management. Further, electronics maybe included in vacuum tubes to disconnect the tubes responsive to overshoot, arcs, or spit.

Referring to FIGS. 13-14, schematic diagrams representing connectionsbetween a high voltage generator and x-ray tubes are shown. Inparticular, FIG. 13 schematically shows a front view of an interface fora high voltage generator and x-ray tubes, and FIG. 14 schematicallyshows a side view of the interface.

In x-ray imaging systems, the high-voltage (HV) generator and the x-raytube are often connected using a flexible HV cable. Such HV cables arepoint-to-point connections, e.g. between a HV generator and an x-raytube. For some applications, the cables are flexible to account forrelative movement of the interconnected devices with respect to eachother. For other applications, such as different components mounted on aCT imaging system, such relative movement may not be utilized, butcommonly, flexible HV cables are used, nonetheless. However, even in thecase where only small distances are bridged, the cable often includes alonger length to be flexible enough to be unplugged. This is inefficientfor systems with many HV devices, such as a multi-spot system usingmultiple x-ray tubes. Thus, FIGS. 13 and 14 schematically show a rigidsupport system 1300 that provides for both the mounting of thecomponents and the distribution of the HV without cables. The rigidsupport system 1300 includes a plurality of connections 1302 configuredto electronically couple individual x-ray tubes 1304 to a rigid supportstructure 1306.

Referring to FIG. 15, a side view of a segment of a high voltagedistribution system (HVDS) 1500 is shown. The HVDS may be integratedinto a rigid support structure, such as the rigid support structure 1306shown by FIGS. 13-14. The HVDS may provide for mounting of componentsand distribution of the high voltage within the same support structure.In this configuration, high voltage may be supplied to the componentswithout the use of cables (e.g., connecting cables). The HVDS may bedisposed within a sealed container filled with an electrical and thermalinsulating medium (e.g., oil). Because the HVDS may not include activeelectronics, a reliability of the HVDS may be increased. In someexamples, additional insulation may be included in conjunction with theoil, such as plastic components formed from polypropylene (PP). FIG. 15shows the insulating plastic components 1502 arranged within the HVDS.In some examples, the plastic components 1502 may have a differentshape. For example, in the example shown by FIG. 15, the plasticcomponents 1502 are shaped as cones that increase a creepage distancethrough the oil. However, in other examples, the plastic components 1502may be shaped to wind around the conductor in a screw-like fashion(e.g., similar to a shape of overlapping insulating tape applied toouter surfaces of a conductor).

Referring to FIG. 16, a schematic of a flat connector 1600 for a highvoltage distribution system is shown. In one example, the flat connector1600 may be used with the HVDS described above with reference to FIG.15. To insulate high-voltage connectors, the high-voltage connectors areoften spaced apart from the live wire and the grounding. In someexamples, the insulation may be achieved by shaping the connector as along rod or with a ‘candlestick’ shape, or by using a flat connectorwhere the insulation is provided on a flat surface. When many componentsare arranged close to each other, the ‘candlestick’ shape may provide atighter spacing. However, connectors shaped as a rod or ‘candlestick,’have an increased depth relative to flat connectors, which maycomplicate packaging conditions.

High-voltage connectors often include oil or grease to reduce an amountof air surrounding the high-voltage connectors, which may increasecreepage distance. Such connectors utilizing oil may include a wellarranged in a horizontal position to the connector to contain the oil.If a well is not desired, grease may be utilized. However, to simplifyassembly and/or production, a connector including neither grease nor oilis contemplated, such as the flat connector 1600 shown by FIG. 16. Theflat connector 1600 includes a high-voltage connection 1602 arranged ata center of the flat connector 1600 and a plurality of insulatingbarriers 1604 arranged circumferentially around the high-voltageconnection 1602. Gaps 1606 between the insulating barriers may permitair to flow out from the flat connector 1600 during conditions in whicha connection is made to the flat connector 1600.

Referring to FIGS. 17-18, another HVDS 1700 is shown. In particular,FIG. 17 shows a front view of the HVDS 1700 and FIG. 18 shows anenlarged side view of interlocking sections of the HVDS. In the exampleshown, each x-ray tube is directly coupled to each adjacent x-ray tube.For example, x-ray tube 1702 is directly coupled to x-ray tube 1704,x-ray tube 1704 is directly coupled to x-ray tube 1706, x-ray tube 1706is directly coupled to x-ray tube 1708, x-ray tube 1708 is directlycoupled to x-ray tube 1710, and x-ray tube 1710 is directly coupled tox-ray tube 1712. Coupling of adjacent x-ray tubes may be performed byinterlocking features of the adjacent x-ray tubes, as shown by FIG. 18(e.g., with protrusion 1802 of x-ray tube 1702 interlocking directlywith recess 1804 of x-ray tube 1704). As the number of x-ray tubesincreases, the number of high-voltage connections also increases. Forexample, the number of high-voltage connections may be a function of thenumber of x-ray tubes (e.g., two high-voltage connections per x-raytube). By connecting the x-ray tubes directly to each other withoutcables, the amount of cables may be greatly reduced or eliminated, whichmay reduce a cost of the system, increase an ease of assembly of thesystem, and/or reduce a size of the system.

The rigid high-voltage distribution systems described above may providefor space savings by significantly reducing the number of high-voltageconnectors used (e.g., from 2 per x-ray tube in the case with cables, to1 per x-ray tube). Additionally, a single connector (e.g., flatconnector 1600) may supply the power to the HV distribution systems. Theoverall high-voltage capacitance may be significantly reduced, which mayincrease performance during dynamic voltage adjustments, such as duringrecovery of HV instabilities or during HV switching.

Referring to FIGS. 19-21, different views of components of another HVDS2000 are shown. In particular, FIG. 19 shows connectors and connectionsof the HVDS 2000 in an uncoupled configuration, FIG. 20 shows theconnectors and connections of the HVDS 2000 in the coupledconfiguration, and FIG. 21 shows example connection geometries of theconnectors and connections of the HVDS 2000.

FIG. 19 shows connector 1920 configured to couple with connection 1900.The connector 1920 may be arranged at a first portion of the HVDS 2000and the connection 1900 may be arranged at an adjacent, second portionof the HVDS 2000. A side profile 1906 of the connector 1902 and a sideprofile 1904 of the connection 1900 are included by FIG. 19 forillustrative purposes. Each of the connection 1900 and the connector1902 may be relatively flat (e.g., mostly planar or disc-shaped). Theconnector 1902 includes a plurality of annular protrusions 1908 that mayengage with counterpart annular recesses 1910 of the connection 1900.

As shown by FIG. 20, the annular protrusions 1908 may be inserted intothe annular recesses 1910 in order to couple the connector 1902 with theconnection 1900. Because the annular recesses 1910 and annularprotrusions 1908 have radial symmetry, the connector 1902 and theconnection 1900 may rotate relative to each other without disengagingthe annular protrusions 1908 from the annular recesses 1910. The annularprotrusions 1908 and annular recesses 1910 may be electricallyconductive such that electrical energy (e.g., electrical current) may betransmitted between the connector 1902 and the connection 1900 duringconditions in which the connector 1902 is engaged with the connection1900. In this configuration, electrical energy may flow between a firstsection 2002 of the HVDS 2000 and a second section 2004 of the HVDS 2000while providing for a relative rotational movement between the firstsection 2002 and the second section 2004. In one example, the firstsection 2002 may be a stationary portion of an imaging system (e.g., arigid support) and the second section 2004 may be a movable portion ofthe imaging system (e.g., an imaging unit). In some examples, theconnection 1900 at the first section 2002 may receive electrical powervia a cable 2008, and the cable 2008 may extend through the firstsection 2002 and into a ground surface 2006 on which the imaging systemsits. The cable 2008 may additionally extend through the ground surface2006 and electrically couple to an electrical power source. Further, theconnector 1902 may be electrically coupled to one or more othercomponents of the imaging system and may provide electrical energy fromthe electrical power source to the other components via cable 2010.

Example interfaces between a connector 2110 and a connection 2112 areshown by FIG. 21. In one example, the connector 2110 may be similar tothe connector 1902 described above, and the connection 2112 may besimilar to the connection 1900 described above. A first interface 2100is shown in which the connector 2110 includes annular protrusions 2101having a square or rectangular profile, and the connection 2112 includesannular recesses 2103 having a counterpart square or rectangularprofile. A second interface 2102 is shown in which the connector 2110includes annular protrusions 2104 having a tapered profile, and theconnection 2112 includes annular recesses 2106 having a counterparttapered profile. The profile of the protrusions and recesses may providea desired coupling quality (e.g., strength) of the connection 2112 andthe connector 2110.

Referring to FIGS. 22-24, various multi-modal imaging systemconfigurations are shown. FIG. 22 shows a first configuration includingan x-ray source 2208 (e.g., a distributed x-ray source unit, similar tothe distributed x-ray source units described above), an x-ray detectorarray 2206 (e.g., similar to the detector arrays described above), and apositron emission tomography (PET) detector 2202.

FIG. 23 shows a second multi-modal imaging system configurationincluding a first PET detector 2302, a second PET detector 2316, a thirdPET detector 2308, a first x-ray source 2304, a second x-ray source2314, a first x-ray detector array 2306, and a second x-ray detectorarray 2312.

FIG. 24 shows a third multi-modal imaging system configuration includinga first x-ray source 2408, a second x-ray detector array 2406, and amagnetic resonance detector 2404.

In some examples, the imaging systems described herein may include themulti-modal configurations described above with reference to FIGS.22-24.

As mentioned above, a stationary CT imaging system may include multiplestationary x-ray focal spots, which may be included in a distributedx-ray source with multiple emitters in a vacuum enclosure, as multiplex-ray sources, or a combination of both. In some examples, the x-raysources or focal spots may extend over an angular range of 360 degreessurrounding a subject or object being imaged (e.g., the subject 127shown in FIG. 1). In another example, the x-ray sources or focal spotsmay extend over a range that is approximately 180 degrees. Further, thestationary CT imaging system may include one or more x-ray detectors(e.g., detector arrays) positioned directly opposite the x-ray sourcesin order to measure x-rays after they penetrate through the subject. Thex-ray detectors may also extend over 360 degrees, 180 degrees, or less,depending on the configuration of the x-ray sources or focal spots andthe configuration of the detector. Further still, single energy ormulti-energy x-ray sources may be used.

As such, FIGS. 25-36 show exemplary embodiments of distributed x-raysource and x-ray detector configurations that may be utilized in animaging unit of a stationary CT imaging system (e.g., the imaging unit123 of the imaging system 100 of FIG. 1). Letters (e.g., “a,” “b,” andthe like) designate multiples of a functionally equivalent component,when included. Further, it may be understood that each distributed x-raysource and x-ray detector configuration may include anti-scatter grids,multiple aperture devices, and/or collimators, examples of which aredescribed herein, at least in some examples. Additionally, it may beunderstood that although the x-ray sources and x-ray detectors areschematically shown as continuous surfaces, it may be understood thatdistinct emitters and/or detector cells may be distributed in arraysacross the surfaces, such as coupled to one or more substrates.

In the examples described below, multiple sources may be activatedsimultaneously. As will be elaborated below, the configurations may besuch that the primary beam of two simultaneously activated sources donot coincide on any detector to avoid confounding or multiplexing. Tominimize scattered radiation, the scan field of view may be reduced, andROI scanning and reconstruction may be performed, such as will bedescribed herein with respect to FIGS. 51-55.

FIGS. 25-30 each show single energy configurations, while FIGS. 31-36each show multi-energy configurations. The multi-energy configurationsinclude operating different x-ray sources, which may be different focalspots or different x-ray tubes, at different voltages. The term “lowenergy” corresponds to an x-ray source operated at a low voltagerelative to “medium energy” and “high energy” x-ray sources. The term“high energy” corresponds to an x-ray source that is operated at ahigher voltage than both the medium energy and low energy x-ray sources.During a scan, the voltage for each x-ray source may not change for agiven x-ray source. Instead, the given x-ray source may be switched on(e.g., powered) or off (e.g., unpowered) as desired, such as describedabove with respect to FIG. 1. It also may be understood that althoughthe following embodiments show configurations having x-ray sources withtwo (e.g., dual-energy) or three different energy levels, theembodiments may include more than two or more than three differentenergies in some examples.

Referring first to FIG. 25, a first exemplary embodiment of a singleenergy x-ray source and detector configuration 2500 is schematicallyshown in a transaxial view 2501 and a lateral view 2503. The x-raysource and detector configuration 2500 includes a distributed x-raysource 2504 and an x-ray detector 2508, which each have a 360 degreerange centered on a central axis 2516, which may be parallel with az-axis that extends directed into the page and directly out of the page.The distributed x-ray source 2504 may be the distributed x-ray sourceunit 104 shown in FIG. 1, for example, and the x-ray detector 2508 maybe the detector array of FIG. 1. The distributed x-ray source 2504 andthe x-ray detector 2508 are both rotationally fixed with respect to thecentral axis 2516. For example, neither the distributed x-ray source2504 nor the x-ray detector 2508 rotates about the central axis 2516.Further, in some examples, neither the distributed x-ray source 2504 northe x-ray detector 2508 translates along the central axis 2516, while inother examples, the distributed x-ray source 2504 and the x-ray detector2508 are translated in tandem to obtain different scan views.

The distributed x-ray source 2504 and the x-ray detector 2508 eachinclude curved, non-planar arrangements in the x-ray source and detectorconfiguration 2500. In the example shown, the distributed x-ray source2504 and the x-ray detector 2508 are both circular in shape, althoughother curved shapes are possible (e.g., oval). Elongated shapes such asthe oval may allow the distributed x-ray source 2504 and the x-raydetector 2508 to better conform to a contour of the subject and increasean angular coverage. Although the schematic representation shows thedistributed x-ray source 2504 and the x-ray detector 2508 havingdifferent diameters in the transaxial view 2501, it may be understoodthat the distributed x-ray source 2504 and the x-ray detector 2508 mayhave a same diameter and may be offset along the central axis 2516 sothat the distributed x-ray source 2504 and the x-ray detector 2508 donot coincide, as shown in the lateral view 2503. For example, thedistributed x-ray source 2504 and the x-ray detector 2508 may havedifferent z-axis positions.

Next, FIG. 26 schematically shows a second exemplary embodiment of asingle energy x-ray source and detector configuration 2600 in atransaxial view 2601 and a lateral view 2603. The x-ray source anddetector configuration 2600 includes a distributed x-ray source 2604 andan x-ray detector 2608, which each have a 180 degree range centered on acentral axis 2616 that is parallel to a z-axis, as described above withrespect to FIG. 25. The distributed x-ray source 2604 may be thedistributed x-ray source unit 104 shown in FIG. 1, for example, and thex-ray detector 2608 may be the detector array of FIG. 1. The distributedx-ray source 2604 and the x-ray detector 2608 are both rotationallyfixed with respect to the central axis 2616. For example, neither thedistributed x-ray source 2604 nor the x-ray detector 2608 rotates aboutthe central axis 2616. Further, in some examples, neither thedistributed x-ray source 2604 nor the x-ray detector 2608 may translatealong the central axis 2616, while in other examples, the distributedx-ray source 2604 and the x-ray detector 2608 are translated in tandemto obtain different scan views.

The distributed x-ray source 2604 and the x-ray detector 2608 eachinclude curved, non-planar arrangements in the x-ray source and detectorconfiguration 2600. In the example shown, the distributed x-ray source2604 and the x-ray detector 2608 are each semi-circular in shape,although other curved shapes are possible that include a varying radialdistance from the central axis 2616 (e.g., half-ovals). The distributedx-ray source 2604 and the x-ray detector 2608 have an overlapping z-axisposition, as shown in the lateral view 2603, and are angularlynon-overlapping with respect to the central axis 2616, as shown in thetransaxial view 2601. For example, the distributed x-ray source 2604 mayextend from 0 to 180 degrees with respect to the central axis 2616, andthe x-ray detector 2608 may extend from 180 to 360 degrees with respectto the central axis 2616. As such, the distributed x-ray source 2604 andthe x-ray detector 2608 do not coincide.

Continuing to FIG. 27, a third exemplary embodiment of a single energyx-ray source and detector configuration 2700 is schematically shown in atransaxial view 2701 and a lateral view 2703. The x-ray source anddetector configuration 2700 includes a central axis 2716 surrounded bytwo distributed x-ray sources 2704 a and 2704 b and two x-ray detectors2708 a and 2708 b. Each distributed x-ray source 2704 a and 2704 b maybe one example of the distributed x-ray source unit 104 shown in FIG. 1,and each x-ray detector 2708 a and 2708 b may be one example of thedetector array 147 of FIG. 1. The distributed x-ray sources 2704 a and2704 b and the x-ray detectors 2708 a and 2708 b are rotationally fixedwith respect to the central axis 2716. For example, none of thedistributed x-ray sources 2704 a and 2704 b and the x-ray detectors 2708a and 2708 b rotates about the central axis 2716. Further, in someexamples, none of the distributed x-ray sources 2704 a and 2704 b andthe x-ray detectors 2708 a and 2708 b may translate along the centralaxis 2716, while in other examples, the distributed x-ray sources 2704 aand 2704 b and the x-ray detectors 2708 a and 2708 b are translated inconcert to obtain different scan views.

The distributed x-ray sources 2704 a and 2704 b and the x-ray detectors2708 a and 2708 b each include planar arrangements in the x-ray sourceand detector configuration 2700. The distributed x-ray sources 2704 aand 2704 b and the x-ray detectors 2708 a and 2708 b are shown having asame length (e.g., longest dimension) in the present example, giving thex-ray source and detector configuration 2700 a square shape. However, inother examples, the x-ray source and detector configuration 2700 may berectangular in shape. For example, the distributed x-ray source 2704 aand the x-ray detector 2708 a may each have a first length that isgreater than a second length of the distributed x-ray source 2704 b andthe x-ray detector 2708 b (or vice versa). Such elongated shapes mayallow the x-ray source and detector configuration 2700 to better conformto a contour of the subject and increase an angular coverage.

In the x-ray source and detector configuration 2700, each distributedx-ray source 2704 a and 2704 b and each x-ray detector 2708 a and 2708 bhas a 90 degree range. Thus, the distributed x-ray sources 2704 a and2704 b have a combined 180 degree range, and the x-ray detectors 2708 aand 2708 b have a combined 180 degree range that is angularlynon-overlapping with the 180 degree range for the distributed x-raysources 2704 a and 2704 b. For example, the distributed x-ray source2704 a is positioned parallel to and directly opposite the x-raydetector 2708 a, and the distributed x-ray source 2704 b is positionedparallel to and directly opposite the x-ray detector 2708 b. As such,the x-ray detector 2708 a is positioned to measure x-rays emitted by thedistributed x-ray source 2704 a, and the x-ray detector 2708 b ispositioned to measure x-rays emitted by the distributed x-ray source2704 b. Further, as shown in the lateral view 2703, the distributedx-ray source 2704 a and the x-ray detector 2708 a have an overlappingz-axis position. It may be understood that the distributed x-ray source2704 b and the x-ray detector 2708 b also have an overlapping z-axisposition with respect to each other and with respect to the distributedx-ray source 2704 a and the x-ray detector 2708 a. Including planardistributed x-ray sources 2704 a and 2704 b and planar x-ray detectors2708 a and 2708 b may enable a post-patient anti-scatter collimator withsepta between detector rows to be used. As a result, scatter rejectionmay be performed efficiently.

Referring now to FIG. 28, a fourth exemplary embodiment of a singleenergy x-ray source and detector configuration 2800 is schematicallyshown in a transaxial view 2801 and a lateral view 2803. The x-raysource and detector configuration 2800 includes a central axis 2816surrounded by three x-ray sources 2804 a 2804 b, and 2804 c and threex-ray detectors 2808 a, 2808 b, and 2808 c. Each x-ray source 2804 a,2804 b, and 2804 c may be one example of the distributed x-ray sourceunit 104 shown in FIG. 1, and each x-ray detector 2808 a, 2808 b, and2808 c may be one example of the detector array of FIG. 1. The x-raysources 2804 a, 2804 b, and 2804 c and the x-ray detectors 2808 a, 2808b, and 2808 c are rotationally fixed with respect to the central axis2816. For example, none of the x-ray sources 2804 a, 2804 b, and 2804 cand the x-ray detectors 2808 a, 2808 b, and 2808 c rotates about thecentral axis 2816. Further, in some examples, none of the x-ray sources2804 a, 2804 b, and 2804 c and the x-ray detectors 2808 a, 2808 b, and2808 c may translate along the central axis 2816, while in otherexamples the x-ray sources 2804 a, 2804 b, and 2804 c and the x-raydetectors 2808 a, 2808 b, and 2808 c are translated in concert to obtaindifferent scan views.

The x-ray sources 2804 a, 2804 b, and 2804 c and the x-ray detectors2808 a, 2808 b, and 2808 c each include curved arrangements such thatthe x-ray source and detector configuration 2800 is circular in shape.However, in other examples, x-ray source and detector configuration 2800may be oval in shape, for example. In the x-ray source and detectorconfiguration 2800, each x-ray source 2804 a, 2804 b, and 2804 c andeach x-ray detector 2808 a, 2808 b, and 2808 c has a 60 degree range.Thus, the x-ray sources 2804 a, 2804 b, and 2804 c have a combined 180degree range, and the x-ray detectors 2808 a, 2808 b, and 2808 c have acombined 180 degree range that is angularly non-overlapping with the 180degree range for the x-ray sources 2804 a and 2804 b. Further, in someexamples, there may be more than three x-ray detector portions and morethan three x-ray source portions.

The x-ray sources 2804 a, 2804 b, and 2804 c alternate with the x-raydetectors 2808 a, 2808 b, and 2808 c about the central axis 2816. Forexample, the x-ray source 2804 a is positioned directly opposite to thex-ray detector 2808 a, the x-ray source 2804 b is positioned directlyopposite the x-ray detector 2808 b, and the x-ray source 2804 c ispositioned directly opposite the x-ray detector 2808 c. As such, thex-ray detector 2808 a is positioned to measure x-rays emitted by thex-ray source 2804 a, the x-ray detector 2808 b is positioned to measurex-rays emitted by the x-ray source 2804 b, and the x-ray detector 2808 cis positioned to measure x-rays emitted by the x-ray source 2804 c.Further, each x-ray source 2804 a, 2804 b, and 2804 c is directlyadjacent to two of the x-ray detectors 2808 a, 2808 b, and 2808 c suchthat the x-ray sources and the x-ray detectors alternate about thecentral axis 2816. Further still, as shown in the lateral view 2803, thex-ray sources and the x-ray detectors have an overlapping z-axisposition (e.g., along the central axis 2816).

Next, FIG. 29 schematically shows a fifth exemplary embodiment of asingle energy x-ray source and detector configuration 2900 in atransaxial view 2901 and a lateral view 2903. The x-ray source anddetector configuration 2900 includes a central axis 2916 surrounded bythree distributed x-ray sources 2904 a 2904 b, and 2904 c and threex-ray detectors 2908 a, 2908 b, and 2908 c. Each distributed x-raysource 2904 a, 2904 b, and 2904 c may be one example of the distributedx-ray source unit 104 shown in FIG. 1, and each x-ray detector 2908 a,2908 b, and 2908 c may be one example of the detector array of FIG. 1.The distributed x-ray sources 2904 a, 2904 b, and 2904 c and the x-raydetectors 2908 a, 2908 b, and 2908 c are rotationally fixed with respectto the central axis 2916. For example, none of the distributed x-raysources 2904 a, 2904 b, and 2904 c and the x-ray detectors 2908 a, 2908b, and 2908 c rotates about the central axis 2916. Further, in someexamples, none of the distributed x-ray sources 2904 a, 2904 b, and 2904c and the x-ray detectors 2908 a, 2908 b, and 2908 c may translate alongthe central axis 2916, while in other examples the distributed x-raysources 2904 a, 2904 b, and 2904 c and the x-ray detectors 2908 a, 2908b, and 2908 c are translated in concert to obtain different scan views.

The distributed x-ray sources 2904 a, 2904 b, and 2904 c and the x-raydetectors 2908 a, 2908 b, and 2908 c each include planar arrangementssuch that the x-ray source and detector configuration 2900 is hexagonalin shape. Although an aspect ratio of the hexagonal shape is 1 in theexample shown, the hexagonal shape may have other aspect ratios in otherexamples. For example, a height of the x-ray source and detectorconfiguration 2900 may be greater than the width. The planarconfiguration of each x-ray detector 2908 a, 2908 b, and 2908 c mayenable an anti-scatter collimator with septa between detector rows to beused, such as mentioned above with respect to FIG. 27. Further, in someexamples, there may be more than three x-ray detector portions and morethan three x-ray source portions.

In the x-ray source and detector configuration 2900, each distributedx-ray source 2904 a, 2904 b, and 2904 c and each x-ray detector 2908 a,2908 b, and 2908 c has a 60 degree range. Thus, the distributed x-raysources 2904 a, 2904 b, and 2904 c have a combined 180 degree range, andthe x-ray detectors 2908 a, 2908 b, and 2908 c have a combined 180degree range that is angularly non-overlapping with the 180 degree rangefor the distributed x-ray sources 2904 a and 2904 b. For example, thedistributed x-ray source 2904 a is positioned directly opposite to thex-ray detector 2908 a, the distributed x-ray source 2904 b is positioneddirectly opposite the x-ray detector 2908 b, and the distributed x-raysource 2904 c is positioned directly opposite the x-ray detector 2908 c.As such, the x-ray detector 2908 a is positioned to measure x-raysemitted by the distributed x-ray source 2904 a, the x-ray detector 2908b is positioned to measure x-rays emitted by the distributed x-raysource 2904 b, and the x-ray detector 2908 c is positioned to measurex-rays emitted by the distributed x-ray source 2904 c. Further, eachdistributed x-ray source 2904 a, 2904 b, and 2904 c is directly adjacentto two of the x-ray detectors 2908 a, 2908 b, and 2908 c such that thex-ray sources and the x-ray detectors alternate about the central axis2916. Further still, as shown in the lateral view 2903, the x-raysources and the x-ray detectors have an overlapping z-axis position(e.g., along the central axis 2916).

FIG. 30 schematically shows a sixth exemplary embodiment of a singleenergy x-ray source and detector configuration 3000 in a transaxial view3001 and a lateral view 3003. The x-ray source and detectorconfiguration 3000 includes a distributed x-ray source 3004 having a 360degree range and an x-ray detector 3008 having a 60 degree range. Thedistributed x-ray source 3004 may be the distributed x-ray source unit104 shown in FIG. 1, for example, and the x-ray detector 3008 may be thedetector array of FIG. 1. The distributed x-ray source 3004 and thex-ray detector 3008 are both centered on a central axis 3016 that isparallel to a z-axis, as described above with respect to FIG. 25. Thedistributed x-ray source 3004 and is rotationally fixed with respect tothe central axis 3016, but the x-ray detector 3008 rotates about thecentral axis 3016, making x-ray source and detector configuration 3000“semi-stationary.” Further, in some examples, neither the distributedx-ray source 3004 nor the x-ray detector 3008 translates along thecentral axis 3016, while in other examples, the distributed x-ray source3004 and the x-ray detector 3008 are translated in tandem to obtaindifferent scan views.

The distributed x-ray source 3004 and the x-ray detector 3008 eachinclude curved, non-planar arrangements in the x-ray source and detectorconfiguration 3000. In the example shown, the distributed x-ray source3004 is circular in shape, and the x-ray detector 3008 is a curve havinga smaller radial distance from the central axis 3016. The distributedx-ray source 3004 and the x-ray detector 3008 have an overlapping z-axisposition, as shown in the lateral view 3003. Although the x-ray sourceand detector configuration 3000 includes the rotating x-ray detector3008, detector costs may be decreased and scatter rejection may beincreased compared with systems that include a rotating x-ray source andx-ray detector. Further, the CT imaging system may be more compact thansystems that include a rotating x-ray source and x-ray detector.

Referring now to FIG. 31, a first exemplary embodiment of a multi-energyx-ray source and detector configuration 3100 is schematically shown in atransaxial view 3101. The x-ray source and detector configuration 3100includes a high energy distributed x-ray source 3104, a low energydistributed x-ray source 3105, and an x-ray detector 3108, which eachhave a 360 degree range centered on a central axis 3116. The high energydistributed x-ray source 3104 and the low energy distributed x-raysource 3105 each may be one example of the distributed x-ray source unit104 shown in FIG. 1, and the x-ray detector 3108 may be the detectorarray of FIG. 1. The central axis 3116 may be parallel with a z-axisthat extends directed into the page and directly out of the page. Thehigh energy distributed x-ray source 3104, the low energy distributedx-ray source 3105, and the x-ray detector 3108 are each rotationallyfixed with respect to the central axis 3116. For example, the highenergy distributed x-ray source 3104, the low energy distributed x-raysource 3105, and the x-ray detector 3108 do not rotate about the centralaxis 3116. Further, in some examples, the high energy distributed x-raysource 3104, the low energy distributed x-ray source 3105, and the x-raydetector 3108 do not translate along the central axis 3116, while inother examples, the high energy distributed x-ray source 3104, the lowenergy distributed x-ray source 3105, and the x-ray detector 3108 aretranslated in concert to obtain different scan views. Multi-energy x-raysource and detector configuration 3100 includes a highest amount ofsource redundancy compared with the configurations that will bedescribed with respect to FIGS. 32-36. However, including such as highamount of source redundancy increases a cost and complexity of thesystem.

The high energy distributed x-ray source 3104, the low energydistributed x-ray source 3105, and the x-ray detector 3108 each includecurved, non-planar arrangements in the x-ray source and detectorconfiguration 3100. In the example shown, the high energy distributedx-ray source 3104, the low energy distributed x-ray source 3105, and thex-ray detector 3108 are all circular in shape, although other curvedshapes are possible (e.g., oval). Although the schematic representationshows the high energy distributed x-ray source 3104, the low energydistributed x-ray source 310, 5 and the x-ray detector 3108 havingdifferent diameters in the transaxial view 3101, it may be understoodthat the high energy distributed x-ray source 3104, the low energydistributed x-ray source 3105, and the x-ray detector 3108 may have asame diameter and may be offset along the central axis 3116 so that thehigh energy distributed x-ray source 3104, the low energy distributedx-ray source 3105, and the x-ray detector 3108 do not coincide, such asdescribed with respect to FIG. 25. For example, each of the high energydistributed x-ray source 3104, the low energy distributed x-ray source3105, and the x-ray detector 3108 may have different z-axis positions.

Multi-energy x-ray source and detector configuration 3100 includes ahighest amount of source redundancy compared with the configurationsthat will be described with respect to FIGS. 32-36. However, includingsuch as high amount of source redundancy increases a cost and complexityof the system. Therefore, other embodiments that include less sourceredundancy while still providing high quality reconstructed images maybe desirable.

Referring next to FIG. 32, a second exemplary embodiment of amulti-energy x-ray source and detector configuration 3200 isschematically shown in a transaxial view 3201. The x-ray source anddetector configuration 3200 includes a high energy distributed x-raysource 3204, a low energy distributed x-ray source 3205, and an x-raydetector 3208. The high energy distributed x-ray source 3204 and the lowenergy distributed x-ray source 3205 each may be one example of thedistributed x-ray source unit 104 shown in FIG. 1, and the x-raydetector 3208 may be the detector array of FIG. 1. The high energydistributed x-ray source 3204 and the low energy distributed x-raysource 3205 each have a 180 degree range centered on a central axis 3216that is parallel to a z-axis, as described above with respect to FIG.31, while the x-ray detector 3208 has a 360 degree range about thecentral axis 3216. The high energy distributed x-ray source 3204, thelow energy distributed x-ray source 3205, and the x-ray detector 3208are each rotationally fixed with respect to the central axis 3216. Forexample, none of the high energy distributed x-ray source 3204, the lowenergy distributed x-ray source 3205, and the x-ray detector 3208rotates about the central axis 3216. Further, in some examples, the highenergy distributed x-ray source 3204, the low energy distributed x-raysource 3205, and the x-ray detector 3208 may not translate along thecentral axis 3216, while in other examples, the high energy distributedx-ray source 3204, the low energy distributed x-ray source 3205, and thex-ray detector 3208 are translated in concert to obtain different scanviews.

The high energy distributed x-ray source 3204, the low energydistributed x-ray source 3205, and the x-ray detector 3208 each includecurved, non-planar arrangements in the x-ray source and detectorconfiguration 3200. In the example shown, the high energy distributedx-ray source 3204 and the low energy distributed x-ray source 3205 areeach semi-circular in shape, although other curved shapes are possiblethat include a varying radial distance from the central axis 3216 (e.g.,half-ovals). Further, the x-ray detector 3208 is circular in the exampleshown, but may be an oval in other examples. The high energy distributedx-ray source 3204 and the low energy distributed x-ray source 3205 mayhave an overlapping z-axis position and are angularly non-overlappingwith respect to the central axis 3216. For example, the high energydistributed x-ray source 3204 may extend from 0 to 180 degrees withrespect to the central axis 3216, and the low energy distributed x-raysource 3205 may extend from 180 to 360 degrees with respect to thecentral axis 3216. As such, the high energy distributed x-ray source3204 and the low energy distributed x-ray source 3205 do not coincide.Further, the x-ray detector 3208 may have a different z-axis positionfrom the high energy distributed x-ray source 3204 and the low energydistributed x-ray source 3205, at least in some examples.

Continuing to FIG. 33, a third exemplary embodiment of a multi-energyx-ray source and detector configuration 3300 is schematically shown in atransaxial view 3301. The x-ray source and detector configuration 3300includes a central axis 3316 surrounded by a high energy x-ray sources3304, a low energy distributed x-ray source 3305, and two x-raydetectors 3308 a and 3308 b. The high energy distributed x-ray source3304 and the low energy distributed x-ray source 3305 each may be oneexample of the distributed x-ray source unit 104 shown in FIG. 1, andthe x-ray detectors 3308 a and 3308 b each may be one example of thedetector array of FIG. 1. The high energy distributed x-ray source 3304,the low energy distributed x-ray source 3305, and the x-ray detectors3308 a and 3308 b are rotationally fixed with respect to the centralaxis 3316. For example, none of the high energy distributed x-ray source3304, the low energy distributed x-ray source 3305, and the x-raydetectors 3308 a and 3308 b rotates about the central axis 3316.Further, in some examples, the high energy distributed x-ray source3304, the low energy distributed x-ray source 3305, and the x-raydetectors 3308 a and 3308 b do not translate along the central axis3316, while in other examples, the high energy distributed x-ray source3304, the low energy distributed x-ray source 3305, and the x-raydetectors 3308 a and 3308 b are translated in concert to obtaindifferent scan views.

The high energy distributed x-ray source 3304, the low energydistributed x-ray source 3305, and the x-ray detectors 3308 a and 3308 beach include planar arrangements in the x-ray source and detectorconfiguration 3300. The high energy distributed x-ray source 3304, thelow energy distributed x-ray source 3305, and the x-ray detectors 3308 aand 3308 b are shown having a same length (e.g., longest dimension) inthe present example, giving the x-ray source and detector configuration3300 a square shape. However, in other examples, the x-ray source anddetector configuration 3300 may be rectangular in shape. For example,the high energy distributed x-ray source 3304 and the x-ray detector3308 a may each have a first length that is greater than a second lengthof the low energy distributed x-ray source 3305 and the x-ray detector3308 b (or vice versa). Such elongated shapes may allow the x-ray sourceand detector configuration 3300 to better conform to a contour of thesubject and increase an angular coverage.

In the x-ray source and detector configuration 3300, each of the highenergy distributed x-ray source 3304, the low energy distributed x-raysource 3305, the x-ray detector 3308 a, and the x-ray detector 3308 bhas a 90 degree range. Thus, the high energy distributed x-ray source3304 and the low energy distributed x-ray source 3305 have a combined180 degree range, and the x-ray detectors 3308 a and 3308 b have acombined 180 degree range that is angularly non-overlapping with the 180degree range for the high energy distributed x-ray source 3304 and thelow energy distributed x-ray source 3305. For example, the high energydistributed x-ray source 3304 is positioned parallel to and directlyopposite the x-ray detector 3308 a, and the low energy distributed x-raysource 3305 is positioned parallel to and directly opposite the x-raydetector 3308 b. As such, the x-ray detector 3308 a is positioned tomeasure x-rays emitted by the high energy distributed x-ray source 3304,and the x-ray detector 3308 b is positioned to measure x-rays emitted bythe low energy distributed x-ray source 3305. Further, the high energydistributed x-ray source 3304, the low energy distributed x-ray source3305, the x-ray detector 3308 a, and the x-ray detector 3308 b may havean overlapping z-axis position due to their non-overlapping angularpositions, such as described above with respect to FIG. 27.

Referring now to FIG. 34, a fourth exemplary embodiment of amulti-energy x-ray source and detector configuration 3400 isschematically shown in a transaxial view 3401. The x-ray source anddetector configuration 3400 includes a central axis 3416 surrounded bythree x-ray sources, including a high energy x-ray source 3404, a lowenergy x-ray source 3405, and a medium energy x-ray source 3407, andthree x-ray detectors 3408 a, 3408 b, and 3408 c. The high energy x-raysource 3404, the low energy x-ray source 3405, and the medium energyx-ray source 3407 each may be one example of the distributed x-raysource unit 104 shown in FIG. 1, and the x-ray detectors 3408 a, 3408 b,and 3408 c each may be one example of the detector array of FIG. 1. Thex-ray sources and the x-ray detectors 3408 a, 3408 b, and 3408 c arerotationally fixed with respect to the central axis 3416. For example,the high energy x-ray source 3404, the low energy x-ray source 3405, themedium energy x-ray source 3407, and the x-ray detectors 3408 a, 3408 b,and 3408 c may not rotate about the central axis 3416. Further, in someexamples, the high energy x-ray source 3404, the low energy x-ray source3405, the medium energy x-ray source 3407, and the x-ray detectors 3408a, 3408 b, and 3408 c may not translate along the central axis 3416,while in other examples the x-ray sources and the x-ray detectors aretranslated in concert to obtain different scan views.

The high energy x-ray source 3404, the low energy x-ray source 3405, themedium energy x-ray source 3407, and the x-ray detectors 3408 a, 3408 b,and 3408 c each include curved arrangements such that the x-ray sourceand detector configuration 3400 is circular in shape. However, in otherexamples, x-ray source and detector configuration 3400 may be oval inshape, for example. In the x-ray source and detector configuration 3400,each of the high energy x-ray source 3404, the low energy x-ray source3405, the medium energy x-ray source 3407 and each x-ray detector 3408a, 3408 b, and 3408 c has a 60 degree range. Thus, the high energy x-raysource 3404, the low energy x-ray source 3405, and the medium energyx-ray source 3407 have a combined 180 degree range, and the x-raydetectors 3408 a, 3408 b, and 3408 c have a combined 180 degree rangethat is angularly non-overlapping with the 180 degree range of the x-raysources. Further, in some examples, there may be more than three x-raydetector portions and more than three x-ray source portions.

The x-ray sources and the x-ray detectors alternate about the centralaxis 3416. For example, the high energy x-ray source 3404 is positioneddirectly opposite to the x-ray detector 3408 a, the low energy x-raysource 3405 is positioned directly opposite the x-ray detector 3408 b,and the medium energy x-ray source 3407 is positioned directly oppositethe x-ray detector 3408 c. As such, the x-ray detector 3408 a ispositioned to measure x-rays emitted by the high energy x-ray source3404, the x-ray detector 3408 b is positioned to measure x-rays emittedby the low energy x-ray source 3405, and the x-ray detector 3408 c ispositioned to measure x-rays emitted by the medium energy x-ray source3407. Further, each x-ray source is directly adjacent to two of thex-ray detectors 3408 a, 3408 b, and 3408 c such that the x-ray sourcesand the x-ray detectors alternate about the central axis 3416. Furtherstill, the x-ray sources and the x-ray detectors may have an overlappingz-axis position (e.g., along the central axis 3416) because they areangularly non-overlapping and therefore do not coincide.

Next, FIG. 35 schematically shows a fifth exemplary embodiment of amulti-energy x-ray source and detector configuration 3500 in atransaxial view 3501. The x-ray source and detector configuration 3500includes a central axis 3516 surrounded by three x-ray sources,including a high energy distributed x-ray source 3504, a low energydistributed x-ray source 3505, and a medium energy distributed x-raysource 3507, and three x-ray detectors 3508 a, 3508 b, and 3508 c. Thehigh energy distributed x-ray source 3504, the low energy distributedx-ray source 3505, and the medium energy distributed x-ray source 3507each may be one example of the distributed x-ray source unit 104 shownin FIG. 1, and the x-ray detectors 3508 a, 3508 b, and 3508 c each maybe one example of the detector array of FIG. 1. The high energydistributed x-ray source 3504, the low energy distributed x-ray source3505, and the medium energy distributed x-ray source 3507 and the x-raydetectors 3508 a, 3508 b, and 3508 c are rotationally fixed with respectto the central axis 3516. For example, none of the x-ray sources and thex-ray detectors 3508 a, 3508 b, and 3508 c may rotate about the centralaxis 3516. Further, in some examples, the high energy distributed x-raysource 3504, the low energy distributed x-ray source 3505, the mediumenergy distributed x-ray source 3507, and the x-ray detectors 3508 a,3508 b, and 3508 c may not translate along the central axis 3516, whilein other examples the x-ray sources and the x-ray detectors aretranslated in concert to obtain different scan views.

The high energy distributed x-ray source 3504, the low energydistributed x-ray source 3505, the medium energy distributed x-raysource 3507, and the x-ray detectors 3508 a, 3508 b, and 3508 c eachinclude planar arrangements such that the x-ray source and detectorconfiguration 3500 is hexagonal in shape. Although an aspect ratio ofthe hexagonal shape is 1 in the example shown, the hexagonal shape mayhave different aspect ratios in other examples. For example, a height ofthe x-ray source and detector configuration 3500 may be greater than thewidth. The planar configuration of each x-ray detector 3508 a, 3508 b,and 3508 c may enable an anti-scatter collimator with septa betweendetector rows to be used, such as mentioned above with respect to FIG.27. Further, in some examples, there may be more than three x-raydetector portions and more than three x-ray source portions.

In the x-ray source and detector configuration 3500, each of the highenergy distributed x-ray source 3504, the low energy distributed x-raysource 3505, and the medium energy distributed x-ray source 3507 andeach x-ray detector 3508 a, 3508 b, and 3508 c has a 60 degree range.Thus, the high energy distributed x-ray source 3504, the low energydistributed x-ray source 3505, and the medium energy distributed x-raysource 3507 have a combined 180 degree range, and the x-ray detectors3508 a, 3508 b, and 3508 c have a combined 180 degree range that isangularly non-overlapping with the 180 degree range of the x-raysources. For example, the high energy distributed x-ray source 3504 ispositioned directly opposite to the x-ray detector 3508 a, the lowenergy distributed x-ray source 3505 is positioned directly opposite thex-ray detector 3508 b, and the medium energy distributed x-ray source3507 is positioned directly opposite the x-ray detector 3508 c. As such,the x-ray detector 3508 a is positioned to measure x-rays emitted by thehigh energy distributed x-ray source 3504, the x-ray detector 3508 b ispositioned to measure x-rays emitted by the low energy distributed x-raysource 3505, and the x-ray detector 3508 c is positioned to measurex-rays emitted by the medium energy distributed x-ray source 3507.Further, each x-ray source is directly adjacent to two of the x-raydetectors 3508 a, 3508 b, and 3508 c such that the x-ray sources and thex-ray detectors alternate about the central axis 3516. Further still,the x-ray sources and the x-ray detectors may have an overlapping z-axisposition (e.g., along the central axis 3516) because they are angularlynon-overlapping.

FIG. 36 schematically shows a sixth exemplary embodiment of amulti-energy x-ray source and detector configuration 3600 in atransaxial view 3601. The x-ray source and detector configuration 3600includes a three high energy x-ray sources 3604 a, 3604 b, and 3604 cand three low energy x-ray sources 3605 a, 3605 b, and 3605 c that eachhave a 60 degree range with respect to a central axis 3616. Thus, thehigh energy x-ray sources 3604 a, 3604 b, and 3604 c have a combinedrange of 180 degrees, and the low energy x-ray sources 3605 a, 3605 b,and 3605 c also have a combined range of 180 degrees. The high energyx-ray sources 3604 a, 3604 b, and 3604 c and the low energy x-raysources 3605 a, 3605 b, and 3605 c each may be one example of thedistributed x-ray source unit 104 shown in FIG. 1. Further, x-ray sourceand detector configuration 3600 includes an x-ray detector 3608 having a60 degree range. The x-ray detector 3608 may be the detector array ofFIG. 1, for example. The high energy x-ray sources 3604 a, 3604 b, and3604 c and the low energy x-ray sources 3605 a, 3605 b, and 3605 c arerotationally fixed with respect to the central axis 3616, but the x-raydetector 3608 rotates about the central axis 3616, making x-ray sourceand detector configuration 3600 “semi-stationary.” Further, in someexamples, the high energy x-ray sources 3604 a, 3604 b, and 3604 c, thelow energy x-ray sources 3605 a, 3605 b, and 3605 c, and the x-raydetector 3608 do not translate along the central axis 3616, while inother examples, the x-ray sources and the x-ray detector 3608 aretranslated in concert to obtain different scan views.

In the example shown, the high energy x-ray sources 3604 a, 3604 b, and3604 c and the low energy x-ray sources 3605 a, 3605 b, and 3605 ctogether form a circular shape, and the x-ray detector 3608 is a curvehaving a smaller radial distance from the central axis 3616. In theexample shown, each high energy x-ray source is directly adjacent to twoof the low energy x-ray sources such that the high energy x-ray sourcesand the low energy x-ray sources alternate about the central axis 3616.For example, the high energy distributed x-ray source 3604 a is adjacentto the low energy x-ray sources 3650 c and 3605 a, the high energydistributed x-ray source 3604 b is adjacent to the low energy x-raysources 3650 a and 3605 b, and the high energy distributed x-ray source3604 c is adjacent to the low energy x-ray sources 3650 b and 3605 c.Further, the high energy x-ray sources 3604 a, 3604 b, and 3604 c, thelow energy x-ray sources 3605 a, 3605 b, and 3605 c, and the x-raydetector 3608 all may have an overlapping z-axis position. Although thex-ray source and detector configuration 3600 includes the rotating x-raydetector 3608, detector costs may be decreased and scatter rejection maybe increased compared with systems that include both a rotating x-raysource and x-ray detector. Further, the CT imaging system may be morecompact than systems that include a rotating x-ray source and x-raydetector.

Still other multi-energy x-ray source arrangements are possible that usethe general geometry of the embodiments shown in FIGS. 31-36. Forexample, each x-ray source may have two targets (anodes) at differentvoltages, such as described above with respect to FIG. 1. FIGS. 37-39Bshow additional exemplary embodiments of a multi-energy x-ray source andx-ray detector configuration that each may be utilized in a stationaryCT imaging system (e.g., the imaging system 100 of FIG. 1). For example,each embodiment shown in FIGS. 37-39B includes 360 degree x-ray sourceand x-ray detector coverage and further includes different energy x-raysources, such as described above with respect to FIG. 31. Thus, FIG. 37particularly highlights the relative arrangement of high energy and lowenergy x-ray sources with respect to each other, and FIGS. 38A-39B showembodiments where the x-ray sources are otherwise controlled ormodulated. Throughout FIGS. 37-39B, components that are similar to, orthe same as, components introduced with respect to FIG. 1 are numberedsimilarly and may function as previously described.

Referring first to FIG. 37, a seventh exemplary embodiment of amulti-energy x-ray source and detector configuration 3700 isschematically shown in a transaxial view 3701. The x-ray source anddetector configuration 3700 includes a plurality of high energy x-raysources 3704, a plurality of low energy x-ray sources 3705, and an x-raydetector 3708, which each have a 360 degree range centered on a centralaxis 3716, such as described above with respect to FIG. 31. For example,the plurality of high energy x-ray sources 3704 and the plurality of lowenergy x-ray sources 3705 are radially distributed with respect to thecentral axis 3716 in an alternating fashion. Each high energydistributed x-ray source 3704 and each low energy distributed x-raysource 3705 may be a separate tube having one or more focal spots, forexample. Further, there is an odd number of both of the high energyx-ray sources 3704 and the low energy x-ray sources 3705 so thatdiametrically opposed tubes have different voltages. For example, eachof the high energy x-ray sources 3704 is directly opposite one of thelow energy x-ray sources 3705 across a diameter of the multi-energyx-ray source and detector configuration 3700. Although there are elevenhigh energy x-ray sources 3704 and eleven low energy x-ray sources 3705illustrated in the example shown in FIG. 37, note that in otherexamples, there may be more or fewer than eleven of each. Further, FIG.37 shows an x-ray beam 3706 being emitted from one of the high energyx-ray sources 3704, although multiple sources may be activatedsimultaneously, such as mentioned above.

Next, FIGS. 38A and 38B show an eighth exemplary embodiment of amulti-energy x-ray source and detector configuration 3800. Themulti-energy x-ray source and detector configuration 3800 is similar tothe multi-energy x-ray source and detector configuration 3700 of FIG. 37except for the addition of a filter 3818. As such, components previouslyintroduced with respect to FIG. 37 are numbered the same and will not bereintroduced. The filter 3818 is organized on a ring-like structure,which rotates with respect to the central axis 3716 to achieve differentfiltration for different x-ray sources. In the example shown, the lowenergy x-ray sources 3705 switch between a “no filtration” state shownin a first transaxial view 3801 of FIG. 38A and a “filtration” stateshown in a second transaxial view 3811 of FIG. 38B. For example, FIG.38A shows an unfiltered beam represented by a solid arrow 3820, whichdoes not pass through filter 3818, while FIG. 38B shows a filtered beamrepresented by a dashed arrow 3822, which passes through the filter3818, due a change in the rotational position of the filter 3818. Thefilter 3818 may remove or attenuate low-energy x-ray photons from theresulting x-ray spectrum, which may decrease an overall x-ray doseprovided to the imaging subject and reduce scatter while not reducingimage quality. For example, the filtered beam represented by the dashedarrow 3822 may have a lower x-ray intensity and a different beam shapecompared with the unfiltered beam represented by the solid arrow 3820.

By varying a frequency of “filtration” and “no filtration” sectionsrelative to the total number of x-ray sources, various source positionsmay not include filtration while other source positions includefiltration at a given rotational position of the filter 3818. This mayproduce a beat pattern in the acquired x-ray spectra. By slowly rotatingthe filter 3818 with respect to the central axis 3716, the locations ofthe filtered and unfiltered x-ray source positions can be modulatedachieve a particular imaging goal.

Further, in some examples, dynamic filtration (that switches betweenfilters for a given x-ray source position) may be used, particularlybecause there is substantial repeat time for a given x-ray source. Forexample, the filter 3818 may include a single filtration material or aplurality of different filtration materials. Each different filtrationmaterial may include one or more of a different composition (e.g., adifferent metal), a different thickness, a different filtered x-rayspectrum, etc. For example, a first filtration section may include afirst filtration material (e.g., aluminum), and a second filtrationsection that is adjacent to the first filtration section may include asecond, different filtration material (e.g., copper). Rotating thefilter 3818 clockwise may place the first filtration section in front ofa given source, while rotating the filter 3818 counterclockwise mayplace the second filtration section in front of the source, for example.It may be understood that although the filter 3818 is shown with respectto multi-energy configuration, the filter 3818 also may be used in asingle energy x-ray source and detector configuration, such as the x-raysource and detector configuration 2500 shown in FIG. 25.

Next, FIGS. 39A and 39B show a ninth exemplary embodiment of amulti-energy x-ray source and detector configuration 3900. Themulti-energy x-ray source and detector configuration 3900 includes aplurality of x-ray sources 3904 and an x-ray detector 3908 that arearranged about a central axis 3916, such as described above with respectto FIG. 25. Further, FIGS. 39A and 39B show an x-ray beam 3906 beingemitted from one of the plurality of x-ray sources 3904, althoughmultiple sources may be activated simultaneously, such as mentionedabove. The plurality of x-ray sources 3904 are switched between a highenergy state shown in transaxial view 3901 of FIG. 39A and a low energystate shown in transaxial view 3911 shown in FIG. 39B. In some examples,all of the plurality of x-ray sources 3904 may be adjusted between thehigh energy state and the low energy state at the same time, such as theexample shown in FIGS. 39A and 39B. For example, each of the pluralityof x-ray sources 3904 may be coupled to a voltage switcher and a dynamicresonance energy recovery generator, such as the voltage switcher 137and the generator array 139 of FIG. 1. In other examples, a firstportion of the plurality of x-ray sources 3904 may be operated with afixed voltage while a second portion of the plurality of x-ray sources3904 may be undergo voltage switching.

In addition to or as an alternative to including different energy x-raysources and/or filtration, a stationary CT imaging system may include aplurality of different x-ray detector types or modules. The selectionand orientation of the different source and detector segments (detectortype, detector width and coverage, detector resolution, source width,source resolution, etc.) may be optimized based on an anatomy to beimaged. For example, the combinations can be adjusted based on typicalmotion patterns (chest wall movement, head movement), an amount of powerused in the imaging (e.g., more power used laterally due to longer pathlengths), and a radiation dose used in the imaging (e.g., lower powerdesired anterior to avoid breast, eyes and thyroid). Further, theprecise spacing and positioning of focal spots and detector cells can bedesigned such that conjugate rays are interlaced to increase a samplingdensity.

As such, FIGS. 40-41 show exemplary embodiments of an x-ray source andx-ray detector configuration that utilize different x-ray detectortypes, either by including separate detector types in a singleconfiguration (e.g., FIG. 40) or by including hybrid detectors thatcombine different detector modules (e.g., FIG. 41). Each of theconfigurations shown in FIGS. 40-41 may be utilized in a stationary CTimaging system (e.g., imaging system 100 of FIG. 1). Letters (e.g., “a,”“b,” and the like) designate multiples of a functionally equivalentcomponent, when included. Further, it may be understood that each x-raysource and x-ray detector configuration may include anti-scatter grids,multiple aperture devices, and/or collimators, examples of which arefurther described herein, at least in some examples. Additionally, itmay be understood that although the x-ray sources and x-ray detectorsare schematically shown as continuous surfaces, it may be understoodthat distinct focal spots and detector cells may be distributed acrossthe surfaces.

Turning now to FIG. 40, a first exemplary embodiment of a multi-detectortype x-ray source and detector configuration 4000 is shown in atransaxial view 4001. The x-ray source and detector configuration 4000includes a central axis 4016 surrounded by three x-ray sources and threex-ray detectors. In particular, the multi-detector type x-ray source anddetector configuration 4000 includes a high resolution distributed x-raysource 4004, two low resolution x-ray sources 4005 a and 4005 b, a highresolution x-ray detector 4008, and two low resolution x-ray detectors4009 a and 4009 b. Each x-ray source may be one example of thedistributed x-ray source unit 104 shown in FIG. 1, and each x-raydetector may be one example of the detector array of FIG. 1.“Resolution” refers to how far apart two structures must be before theyare observed as separate structures in the resulting image (e.g.,spatial resolution). The two structures may be closer together whilestill being observed as two structures in the resulting image in highresolution compared with low resolution. The high resolution distributedx-ray source 4004, the low resolution x-ray sources 4005 a and 4005 b,the high resolution x-ray detector 4008, and the low resolution x-raydetectors 4009 a and 4009 b are all rotationally fixed with respect tothe central axis 4016 and have a geometry similar to that describedabove with respect to FIGS. 29 and 35.

The high resolution distributed x-ray source 4004 is positioned directlyopposite to the high resolution x-ray detector 4008 so that the highresolution x-ray detector 4008 is positioned to detect x-rays emitted bythe high resolution distributed x-ray source 4004. Similarly, the lowresolution distributed x-ray source 4005 a is positioned directlyopposite to the low resolution x-ray detector 4009 a, and the lowresolution distributed x-ray source 4005 b is positioned directlyopposite to the low resolution x-ray detector 4009 b. In this way, theresolution of each x-ray detector is positioned to detect x-rays from asource having a matched resolution. Further, the low resolution x-raysources 4005 a and 4005 b and the low resolution x-ray detectors 4009 aand 4009 b may comprise larger coverage or wider segments and the highresolution distributed x-ray source 4004 and the high resolution x-raydetector 4008 may comprise narrower or smaller coverage segments. Forexample, the high resolution distributed x-ray source 4004 may havesmaller focal spots (e.g., 0.7 mm focal spots) compared with the lowresolution x-ray sources 4005 a and 4005 b (e.g., 1.2 mm focal spots).The smaller focal spots provide good spatial resolution, while thelarger focal spots of the low resolution x-ray sources 4005 a and 4005 bprovide an increased signal-to-noise ratio compared with the smallerfocal spots of the high resolution distributed x-ray source 4004.Similarly, the high resolution x-ray detector 4008 may include smallerdetector cells with larger gaps (e.g., partitions) in between comparedwith the low resolution x-ray detectors 4009 a and 4009 b. In someexamples, the high resolution x-ray detector 4008 is a photon countingdetector module, while the low resolution x-ray detectors 4009 a and4009 b are each a scintillator-based detector module, such as discussedabove with respect to FIG. 1 and elaborated below with respect to FIG.41.

As such, the multi-detector type x-ray source and detector configuration4000 includes lower resolution and higher resolution segments to vary animage quality produced during imaging. For example, the high resolutionx-ray detector 4008 paired with the high resolution distributed x-raysource 4004 may have increased resolution but a reduced overalldetection efficiency compared with the low resolution x-ray detectors4009 a and 4009 b due to the larger gaps between the smaller detectorcells. Conversely, the low resolution x-ray detectors 4009 a and 4009 bpaired with the low resolution x-ray sources 4005 a and 4005 b mayproduce images with a lower resolution but a higher detection efficiencydue to the smaller gaps between detector cells. In some examples, thehigher resolution images and lower resolution images may be combinedusing a deep learning network to produce an overall composite diagnosticimage with an increased signal-to-noise ratio (from the lower resolutionimages generated from measurements of beams produced by the lowresolution x-ray sources 4005 a and 4005 b by the low resolution x-raydetectors 4009 a and 4009 b) and an increased spatial resolution (fromthe higher resolution images generated from measurements of beamsproduced by the high resolution distributed x-ray source 4004 by thehigh resolution x-ray detector 4008), such as according to the methodsof FIGS. 53 and 55.

However, instead of having dedicated x-ray source and detector segmentsfor high resolution and low resolution imaging, higher resolution andlower resolution components may be distributed throughout the x-raysource and detector segments. Continuing to FIG. 41, a second exemplaryembodiment of a multi-detector type x-ray source and detectorconfiguration 4100 is shown in a transaxial view 4101. The x-ray sourceand detector configuration 4100 includes a central axis 4116 surroundedby three distributed x-ray sources 4104 a 4104 b, and 4104 c and threex-ray detectors 4108 a, 4108 b, and 4108 c. Each distributed x-raysource 4104 a, 4104 b, and 4104 c may be one example of the distributedx-ray source unit 104 shown in FIG. 1, and each x-ray detector 4108 a,4108 b, and 4108 c may be one example of the detector array of FIG. 1.The distributed x-ray sources 4104 a, 4104 b, and 4104 c and the x-raydetectors 4108 a, 4108 b, and 4108 c are rotationally fixed with respectto the central axis 4116 and have a geometry similar to that describedabove with respect to FIGS. 29 and 35.

In the multi-detector type x-ray source and detector configuration 4100,each distributed x-ray source 4104 a, 4104 b, and 4104 c comprisesalternating smaller (higher resolution) and larger (lower resolution)focal spots, and each x-ray detector 4108 a, 4108 b, and 4108 ccomprises alternating scintillator-based detector modules (or cells) andphoton counting (or direct conversion) modules (or cells). The photoncounting modules are energy-resolving x-ray detectors that count thenumber of incoming photons and directly measure photon energy. Thescintillator-based detector modules are energy-integrating detectorsthat convert x-rays into visible light and then then measure the amountof incident light. The two detector types may have a different spatialresolution, sensitivity, and/or signal-to-noise ratio. For example, thephoton counting modules may have an increased spatial resolutioncompared with the scintillator-based detector modules. As such,measurements from the photon counting modules may produce higherresolution images, particularly when measuring beams produced by thesmaller focal spots, and measurements from the scintillator-baseddetector modules may produce lower resolution, lower noise images,particularly when measuring beams produced by the larger focal spots.The higher and lower resolution images may be combined using a deeplearning network, such as mentioned above with respect to FIG. 40. Assuch, the multi-detector type x-ray source and detector configuration4100 may have high flexibility for the quality of images produced.

In conventional x-ray and non-stationary CT imaging systems, primaryx-rays are produced from a single focal point, transmitted through animaging subject (e.g., a patient), and detected by a detector. Incontrast, scattered radiation is secondary radiation produced by thedeflection of x-rays by the imaging subject. In such systems, it iseffective to use an anti-scatter grid or post-patient collimator toreject x-rays that have a different incidence angle than the primaryx-rays, thereby rejecting scattered radiation. However, all of the abovex-ray source and detector configurations described with respect to FIGS.25-41 include distributed x-ray sources and/or multiple x-ray sources,and each detector cell is positioned to detect primary x-raysoriginating from multiple x-ray focal spots. Hence, the primary x-raysmay have a wide range of incidence angles, making it difficult to usetraditional stationary anti-scatter grids or collimators. Further, asthe amount of tissue or other substance that is being penetrated by theprimary beam(s) increases, the greater the incidence of scatteredradiation. Therefore, approaches that mitigate scattered radiation(e.g., prevent, reject, and/or correct for the scattered radiation) instationary CT imaging systems are desired.

As such, FIGS. 42A-50 show exemplary embodiments of x-ray source andx-ray detector configurations that may be utilized in an imaging unit ofa stationary CT imaging system (e.g., the imaging unit 123 of theimaging system 100 of FIG. 1). Letters (e.g., “a,” “b,” and the like)designate multiples of a functionally equivalent component, whenincluded. Additionally, it may be understood that although x-raydetectors are schematically shown as continuous surfaces, it may beunderstood that distinct detector cells may be distributed in arraysacross the surfaces, such as coupled to one or more substrates. Further,it may be understood that the following embodiments may be combined withvarious filters and/or post-patient collimators or anti-scatter grids,examples of which are described herein.

In one approach, a solid angle of an incident x-ray beam may be reducedto reduce a scatter-to-primary ratio. The scatter-to-primary ratiorefers to an energy of scattered radiation divided by an energy ofprimary x-ray beam energy striking a same location on a detector.Turning to FIGS. 42A and 42B, x-ray beam truncation is schematicallyshown in an exemplary embodiment of a distributed x-ray source anddetector configuration 4200. The distributed x-ray source and detectorconfiguration 4200 includes a plurality of focal spots of a distributedx-ray source (e.g., the distributed x-ray source unit 104) and detectorcells arranged about a central axis 4216. In the example shown, onlythree of the focal spots—a first focal spot 4204 a, a second focal spot4204 b, and a third focal spot 4204 c—are labeled for illustrativeclarity, and the detector cells are represented schematically by adetector array 4208, which may be the detector array 147 of FIG. 1, forexample.

FIG. 42A shows a first transaxial view 4201, where the first focal spot4204 a is emitting a partial fan beam 4206 a. A range of a full fan beam4210 is shown for comparison by dashed lines. FIG. 42B shows a secondtransaxial view 4211, where the second focal spot 4204 b is emitting apartial fan beam 4206 b. Because scattered radiation is proportional toa portion of the imaging subject being irradiated at a given moment, bytruncating the x-ray beam, such as by using only the partial fan beam4206 a in FIG. 42A and the partial fan beam 4206 b in FIG. 42B, thescatter-to-primary ratio may be reduced. For example, different focalspots can be collimated in different ways, such that the combination ofall of the partial fan beams still provides relatively complete data.For example, the first focal spot 4204 a may be collimated to emit arelative angular range of −30 to −10 degrees, the second focal spot 4204b may be collimated to emit a relative angular range of −10 to +10degrees, and the third focal spot 4204 c may be collimated to emit arelative angular range of +10 to +30 degrees. Further, by reducing theangular range emitted from each focal spot relative to the full fan beam4210, the focal spots may have a larger thermal length and stillpreserve a small optical focal spot size.

In some examples, the collimation for each focal spot may be adjustable.Continuing to FIG. 43, an exemplary embodiment of a distributed x-raysource and detector configuration 4300 including an adjustablecollimator 4314 is shown in a transaxial view 4301. The distributedx-ray source and detector configuration 4300 includes a plurality offocal spots 4304, a detector array 4308, and the adjustable collimator4314 arranged about a central axis 4316. The adjustable collimator 4314is a pre-patient (e.g., imaging subject) collimator and includes aplurality of collimator portions 4320 and 4322 arranged in pairs 4324with respect to each focal spot 4304 and distributed on an actuator 4318about the central axis 4316. An inset box 4303 particularly shows onepair 4324 of collimator portions 4320 and 4322 with respect to one focalspot 4304. For example, the collimator portions 4320 may shape (e.g.,narrow) an x-ray beam 4306 emitted from the corresponding focal spot4304 in a first direction, and the collimator portions 4322 may shapethe x-ray beam 4306 emitted from the corresponding focal spot 4304 in asecond direction, different than the first direction. For example, thesecond direction may be opposite to the first direction. For example,the first direction may be to the right side of the imaging subject,while the second direction is to the left side of the imaging subject.The collimator portions 4320 and 4322 may each be comprised of an x-rayabsorbing material, such as lead or tungsten. Further, the adjustablecollimator 4314 is positioned to block a portion of the x-ray beam 4306emitted from each focal spot 4304 before passing through the imagingsubject, unlike post-patient, pre-detector collimators, which may blockor reduce scatter radiation detection at the detector array 4308.

The actuator 4318 may rotate with respect to the central axis 4316 tomove each pair 4324 with respect to the corresponding focal spot 4304 inorder to adjust a relative angular range of the x-ray beam 4306. In someexamples, the actuator 4318 may comprise a first ring-shaped actuatorcoupled to the collimator portions 4320, and not to the collimatorportions 4322, and a second ring-shaped actuator coupled to thecollimator portions 4322, and not the collimator portions 4320. Anoperator may adjust the first ring-shaped actuator to move thecollimator portions 4320 relative to the focal spots 4304 and adjust thesecond ring-shaped actuator to move the collimator portions 4322relative to the focal spots 4304. In this way, the collimator portions4320 and the collimator portions 4322 may be separately controlled toadjust the relative angular range of the x-ray beam 4306 emitted fromeach focal spot 4304. Further, the adjustable collimator 4314 may reducethe relative angular range of the x-ray beam 4306 relative to that of afull x-ray beam 4310 represented by dashed lines, thereby reducing thescatter-to-primary ratio.

As will be elaborated below with respect to FIG. 52, in some examples,narrow x-ray beam measurements may be alternated with wide beammeasurements from the same focal spot 4304. Narrow beam projectionshaving less scatter, such as those obtained by measuring x-ray beam4306, may be subtracted from wide beam projections having more scatter,such as those obtained from measuring full x-ray beam 4310, to obtain anestimate of the scatter from portions outside of the narrow x-ray beam.

In a further example, the pre-patient collimator may instead break eachx-ray beam into a series of narrow fan beams. Turning now to FIG. 44, anexemplary embodiment of a distributed x-ray source and detectorconfiguration 4400 including a collimator 4414 is shown in a transaxialview 4401. The distributed x-ray source and detector configuration 4400includes a plurality of focal spots 4404 (only one of which is labeledfor illustrative clarity), a detector array 4408, and the collimator4414 arranged about a central axis 4416. The collimator 4414 is apre-patient (e.g., imaging subject) collimator that includes a pluralityof openings that divide an x-ray beam emitted from one focal spot 4404into a plurality of narrow fan beams 4406 a, 4406 b, and 4406 c.Although the collimator 4414 is shown with respect to one focal spot4404, it may be understood that all or some of the focal spots 4404 mayinclude similar collimators. Further, although three narrow fan beams4406 a, 4406 b, and 4406 c are shown, the collimator 4414 may break thex-ray beam into more or fewer than three narrow fan beams. However,breaking the x-ray beam into a plurality of narrow fan beams mayincrease penumbra (e.g., a zone of partial intensity x-rays around acentral zone of full intensity x-rays), which may affect a dose deliveryaccuracy.

As still another example, a focal spot itself may be moved to change afan angle or angular range of an x-ray beam. FIG. 45 schematically showsperforming scatter measurements while adjusting a fan angle of an x-raybeam emitted from a focal spot of a stationary CT imaging system. FIG.45 shows a first lateral view 4503 and a second lateral view 4513, whichmay correspond to different times and operational modes of thestationary CT imaging system. For example, the first lateral view 4503includes operating the stationary CT imaging system in a patient imagingmode, and the second lateral view 4513 includes operating the stationaryCT imaging system in a scatter measurement mode. The lateral views showa first focal spot 4504 a, a second focal spot 4504 b, a first detectorcell 4508 a, and a second detector cell 4508 b distributed about acentral axis 4516. The first focal spot 4504 a, the second focal spot4504 b, the first detector cell 4508 a, and the second detector cell4508 b may be arranged in any of the x-ray source and detectorconfigurations described with respect to FIGS. 25-36, for example.

While operating in the patient imaging mode shown in first lateral view4503, the first focal spot 4504 a emits a higher energy x-ray beam 4506that has a beam center (e.g., isocenter) 4512 directed to a centralpoint of the first detector cell 4508 a. For example, the beam center4512 has a first angle 4514 with respect to an axis that is parallel tothe central axis 4516 and extends from the focal spot 4504 a. Becausethe beam center 4512 is centered on the first detector cell 4508 a,substantially all of the first detector cell 4508 a measures primaryradiation from the higher energy x-ray beam 4506.

While operating in the scatter measurement mode shown in second lateralview 4513, the first focal spot 4504 a emits a lower energy x-ray beam4505 that has a beam center 4511 directed to an end of the firstdetector cell 4508 a. For example, the beam center 4511 has a secondangle 4515 with respect to the axis extending from the focal spot 4504 ain the direction of the central axis 4516. The second angle 4515 isgreater than the first angle 4514. The first focal spot 4504 a isrotated in the second lateral view 4513 compared with the first lateralview 4503 in order to direct the beam center 4511 of the lower energyx-ray beam 4505 at the second angle 4515. Because the beam center 4511is directed at the edge of the first detector cell 4508 a, a portion ofthe first detector cell 4508 a does not measure primary radiation fromthe lower energy x-ray beam 4505 and may instead measure scatterradiation. The lower energy x-ray beam 4505 may be used during thescatter measurement mode (instead of the higher energy x-ray beam 4506used in the patient imaging mode) in order to reduce a radiation dosedelivered to an imaging subject. Further, only a subset of focal spots,such as the first focal spot 4504 a and not the second focal spot 4504b, may be used to perform the scatter measurement in order to furtherdecrease the radiation dose. Note that although FIG. 45 includes anexample of moving the focal spot, a collimator may be similarly used tochange the fan angle of the x-ray beam in the longitudinal directionalong the central axis 4516 between the patient imaging mode and thescatter measurement mode.

As still another example, an imaging unit may additionally oralternatively include post-patient, pre-detector component to attenuatescatter. Turning to FIG. 46, a schematic illustration of a multi-layeraperture device (MAD) 4614 is shown with respect to a detector array4608, a first focal spot 4604 a, a second focal spot 4604 b, and a thirdfocal spot 4604 c at three different positions. For example, the firstfocal spot 4604 a, the second focal spot 4604 b, and the third focalspot 4604 c may be included in a distributed x-ray source (e.g., thedistributed x-ray source unit 104 of FIG. 1), and the detector array4608 may be the detector array 147. The MAD 4614 may be the multi-layeraperture device 133 of FIG. 1, for example. The MAD 4614 is comprised ofa plurality of layers (e.g., rows) 4614 a, 4614 b, 4614 c, 4614 d, and4614 e. Although five layers are shown, in other examples, there may bemore or fewer than five layers. Each layer includes a plurality ofapertures or openings separated by an x-ray blocking material, such asan x-ray absorbing metal (e.g., lead). The openings of each layer arealigned with each other in an adjustable manner. For example, each layer4614 a, 4614 b, 4614 c, 4614 d, and 4614 e translates relative to theother layers to adjust an angle of the openings. Adjusting the alignmentof the openings may adjust an incident angle of x-ray radiation that maypass through the MAD 4614.

FIG. 46 shows the MAD 4614 in a first position 4601, a second position4611, and a third position 4621. For example, the first position 4601may be a left-slanted position having openings positioned at a firstangle (e.g., −30 degrees) relative to an axis extending between a givenfocal spot and a directly opposite detector cell of the detector array147, the second position 4611 may be a vertical position having theopenings positioned at a second angle (e.g., 0 degrees) relative to theaxis, and the third position 4621 may be a right-slanted position havingthe openings positioned at a third angle (e.g., 30 degrees) relative tothe axis. For example, the plurality of layers 4614 a, 4614 b, 4614 c,4614 d, and 4614 e may be moved in concert to adjust the incident angleof radiation that is received by the detector array 4608.

For example, a first x-ray beam 4606 a emitted from the first focal spot4604 a is aligned with the slant (e.g., angle) of the MAD 4614 while theMAD 4614 is in the first position 4601. As a result, the first x-raybeam 4606 a reaches the detector array 4608 and is not blocked by theMAD 4614. In contrast, a second x-ray beam 4606 b emitted from thesecond focal spot 4604 b and a third x-ray beam 4606 c emitted from thethird focal spot 4604 c are not aligned with the slant of the MAD 4614in the first position 4601. As a result, the second x-ray beam 4606 band the third x-ray beam 4606 c are both blocked by the MAD 4614, whichalso blocks scattered radiation 4605. Because the second x-ray beam 4606b, the third x-ray beam 4606 c, and the scattered radiation 4605 areblocked by the MAD 4614 in the first position 4601, they are notdetected by the detector array 4608.

While the MAD 4614 is in the second position 4611, the second x-ray beam4606 b is aligned with the slant of the MAD 4614, while the first x-raybeam 4606 a and the third x-ray beam 4606 c are not. As a result, thesecond x-ray beam 4606 b emitted from the second focal spot 4604 breaches the detector array 4608 and is not blocked by the MAD 4614. Incontrast, the first x-ray beam 4606 a, the third x-ray beam 4606 c, andthe scattered radiation 4605 are blocked by the MAD 4614 and are notdetected by the detector array 4608.

While the MAD 4614 is in the third position 4621, the third x-ray beam4606 c is aligned with the slant of the MAD 4614, while the first x-raybeam 4606 a and the second x-ray beam 4606 b are not. As a result, thethird x-ray beam 4606 c emitted from the third focal spot 4604 c reachesthe detector array 4608 and is not blocked by the MAD 4614. In contrast,the first x-ray beam 4606 a, the second x-ray beam 4606 b, and thescattered radiation 4605 are blocked by the MAD 4614 and are notdetected by the detector array 4608.

Still other approaches may be used for measuring scatter. An exemplaryembodiment of a distributed x-ray source and detector configuration 4700is shown in a transaxial view 4701. The distributed x-ray source anddetector configuration 4700 comprises a plurality of focal spots, whichmay be included in a distributed x-ray source (e.g., the distributedx-ray source unit 104 of FIG. 1), and a detector array 4708 arrangedabout a central axis 4716. Only one focal spot 4704 is labeled forillustrative clarity. The distributed x-ray source and detectorconfiguration 4700 further comprises a plurality of modulators 4714 a,4714 b, and 4714 c. The plurality of modulators 4714 a, 4714 b, and 4714c each comprise a spatially variant x-ray attenuating material and arepositioned between the distributed x-ray source and an imaging subject(e.g., the subject 127 of FIG. 1). For example, the x-ray attenuatingmaterial may be a semi-transparent blocker that is arranged in themodulator in a known geometric fashion, such as in a grid, a stipe, or acheckerboard pattern, for example. As such, selective portions of anx-ray beam are hardened by passing through the attenuating materials inone of the plurality of modulators 4714 a, 4714 b, and 4714 c, whichselectively filter out lower energy photons.

In the example shown in FIG. 47, after passing through the modulator4714 a, an x-ray beam 4706 emitted from the focal spot 4704 has hardenedbeam portions 4705, only one of which is labeled for illustrativeclarity. The hardened beam portions 4705 have an increased averagephoton energy due to the lower energy photons being filtered out by theattenuating materials, which is detected at distinct detector cellsand/or pixel locations of the detector array 4708. This results in aprimary radiation detection pattern that is more strongly separated fromscatter than when the x-ray beam 4706 does not pass through themodulator 4714 a. For example, the scattered radiation may have a lowerenergy than the hardened beam portions 4705, making it easier toidentify scattered radiation from the primary beam signal. The primarybeam signal from the x-ray beam 4706 may be separated from the scattersignal via demodulation principles, for example.

Further, the plurality of modulators 4714 a, 4714 b, and 4714 c may bepositioned in front of a portion of the focal spots for an accuratescatter measurement at those focal spots. For other views or primarybeams that do no undergo modulation, the scatter may be estimated byinterpolation or using the accurate scatter measurements from nearbyfocal spots. By including modulators in front of a portion of the focalspots, a cost and complexity of the distributed x-ray source anddetector configuration 4700 may be decreased.

However, in other examples, scatter measurements may be performed atdetector areas that are not receiving primary x-rays. For example,turning to FIG. 48, an exemplary embodiment of a distributed x-raysource and detector configuration 4800 is shown in a transaxial view4801. The distributed x-ray source and detector configuration 4800comprises a plurality of focal spots, which may be included in adistributed x-ray source (e.g., the distributed x-ray source unit 104 ofFIG. 1), and a detector array 4808 arranged about a central axis 4816.Only one focal spot 4804 is labeled for illustrative clarity. In theexample shown in FIG. 48, an x-ray beam 4806 is emitted from the focalspot 4804 and is directed to a first region 4810 of the detector array4808. Thus, detector cells within the first region 4810 of the detectorarray 4808 measure the primary radiation of the x-ray beam 4806.

Detector cells within a second region 4812 of the detector array 4808,which is outside of the first region 4810, do not receive the primaryradiation of the x-ray beam 4806. For example, the second region 4812may comprise any portion of the detector array 4808 that is outside ofthe x-ray beam 4806. Instead, the detector cells within the secondregion 4812 may detect scattered radiation. Therefore, the detectorcells within the second region 4812 may perform scatter measurements,which may be processed with analytic, Monte Carlo, and/or deep learningscatter estimation/correction algorithms. For example, a deep learningscatter estimation algorithm may use both the primary and scattertransmission profiles, a corresponding attenuation profile, and adjacentscatter measurements as inputs and may output an estimated scatterprofile. Similarly, a deep learning scatter correction algorithm may useboth the primary and scatter transmission profiles, the correspondingattenuation profile, and the adjacent scatter measurements as inputs andmay output an estimate of a scatter-corrected primary profile. Such deeplearning networks use ground truth data for training. A specializedscatter measurement acquisition protocol (e.g., using smaller cone orfan angles) may be used to reduce scatter when acquiring such data.

Further, because scatter profiles change slowly from one view to thenext, regularization can be performed in the view direction, or scattercan be estimated for only a few view angles and interpolated. Inaddition, those scatter measurements can also be used to perform scatterimaging, such as for reconstructing images representing the (primarilyCompton) scatter cross-section in the imaging subject. Similarly, thedetector cells in the second region 4812 that are not receiving the(primary) x-ray beam 4806 can be used for fluorescence imaging whenphoton-counting detectors are used.

However, because the scatter measurements are only measured outside ofthe x-ray beam 4806, there could be an inaccurate scatter estimationcloser to a center of the beam. Therefore, in some examples, x-rayblockers may be used to measure scatter at additional sample pointscloser to a center of the x-ray beam, and using the additional samplepoints may increase an accuracy of the estimation or interpolationdiscussed above.

For example, an exemplary embodiment of a distributed x-ray source anddetector configuration 4900 is shown in a transaxial view 4901. Thedistributed x-ray source and detector configuration 4900 comprises aplurality of focal spots, which may be included in a distributed x-raysource (e.g., the distributed x-ray source unit 104 of FIG. 1), and adetector array 4908 arranged about a central axis 4916. Only one focalspot 4904 is labeled for illustrative clarity. The distributed x-raysource and detector configuration 4900 further comprises x-ray blockers4914. The x-ray blockers 4914 are positioned between the distributedx-ray source and an imaging subject (e.g., the subject 127 of FIG. 1)and fully block primary x-ray beams. In the example shown in FIG. 49,the x-ray blockers 4914 are arranged in an arc in front of a portion ofthe focal spots. However, in other examples, the x-ray blockers 4914 maybe positioned in front of all of the focal spots. Although five x-rayblockers 4914 are shown, there may be more than five or fewer than fivex-ray blockers 4914 in other examples. The x-ray blockers 4914 may becomprised of lead, for example, or another material that absorbs andscatters x-ray radiation without letting it pass through.

In the example shown in FIG. 49, an x-ray beam 4906 emitted from thefocal spot 4904 contacts one x-ray blocker 4914 a of the x-ray blockers4914. As a result, the x-ray beam 4906 is divided into two portions witha primary beam-free region 4910 positioned there between. Scattermeasurements may be obtained in the primary beam-free region 4910 inaddition to or as an alternative to acquiring scatter measurements in aregion of the detector array 4908 outside of the x-ray beam 4906 (e.g.,the second region 4812 described above with respect to FIG. 48).However, the primary beam-free region 4910 produced by the x-ray blocker4914 a results in some missing primary beam measurements, which may berecovered by using deep learning interpolation or iterativereconstruction, an example of which is described herein with respect toFIG. 57.

Because a complexity of a stationary CT imaging system increases with anumber of focal spots, it may be desirable to reduce the number of focalspots compared with a traditional CT imaging system. For example, thestationary CT imaging system may have tens or hundreds of focal spots,resulting in sparse view sampling compared to conventional CT imaging(e.g., approximately 1,000 views). Although FIGS. 42A-44 and 49-47 showthe focal spots uniformly distributed about a central axis of each x-raysource and detector configuration, in some examples, the view samplingmay be non-uniform.

Referring to FIG. 50, a transaxial view 5001 schematically shows anexemplary embodiment of an x-ray source and detector configuration 5000that may be included in an imaging unit of a stationary CT imagingsystem (e.g., the imaging unit 123 of the imaging system 100 of FIG. 1).The x-ray source and detector configuration 5000 includes an x-raydetector 5008 and a distributed x-ray source 5007. The distributed x-raysource 5007 may be the distributed x-ray source unit 104 of FIG. 1, forexample, and the x-ray detector 5008 may be the detector array 147 ofFIG. 1. The distributed x-ray source 5007 and the x-ray detector 5008are shown as each having a semi-circular, arched arrangement, similar tothe geometry described with respect to the x-ray source and detectorconfiguration 2600 of FIG. 26. However, in other examples, thedistributed x-ray source 5007 and the x-ray detector 5008 may each havea 360 degree range, such as described with respect to the x-ray sourceand detector configuration 2500 of FIG. 25. The distributed x-ray source5007 includes plurality of x-ray sources 5004 a, 5004 b, 5004 c, 5004 d,and 5004 e, and each x-ray source includes a multiple focal spots. Forexample, each of the x-ray sources 5004 a, 5004 b, 5004 c, 5004 d, and5004 e may be a separate x-ray tube. In the example shown in FIG. 50,each x-ray source 5004 a, 5004 b, 5004 c, 5004 d, and 5004 e includesfour focal spots, but the number of focal spots may be greater than fouror less than four.

The x-ray source 5004 a includes focal spots 5005 a that produce views5006 a. For example, each focal spot 5005 a produces one of the views5006 a. Similarly, x-ray source 5004 b includes focal spots 5005 b thatproduce views 5006 b, x-ray source 5004 c includes focal spots 5005 cthat produce a set of views 5006 c, x-ray source 5004 d includes focalspots 5005 d that produce a set of views 5006 d, and x-ray source 5004 eincludes focal spots 5005 e that produce a set of views 5006 e. As such,the view sampling is locally dense, but sparse overall. For example, theset of views 5006 a includes four views that are locally close to eachother, but spaced apart from the set of views 5006 b.

The focal spot spacing may be optimized for optimal view sampling. Forexample, opposite views may be interlaced such that the redundancy inconjugate rays is minimized. This may be achieved, for example, by usingan odd number of focal spots (or tubes) uniformly spread across 360degrees. For instance, focal spots may be positioned at 0° and 8° and onthe opposite side a focal spot may be positioned at −4°+180°, 4°+180°,and 12°+180°. Optionally, the tube of each x-ray source 5004 a, 5004 b,5004 c, 5004 d, and 5004 e may be oriented such that the segments offocal spots in each tube do not line up along the arch of thedistributed x-ray source 5007, but can be tilted to be parallel to alongitudinal axis or somewhere in between (oblique). In some examples,the position of the focal spots within each x-ray source 5004 a, 5004 b,5004 c, 5004 d, and 5004 e may vary continuously by steering an electronbeam and sweeping along the target.

FIG. 51 shows a flow chart illustrating a method 5100 for carrying out aCT scan using a stationary CT imaging system, which may be the imagingsystem 100 shown in FIG. 1. The stationary CT imaging system may includeany of the x-ray source and detector configurations described withrespect to FIGS. 25-50, for example. The method 5100 and other methodsincluded herein may be carried out according to instructions stored innon-transitory memory of one or more computing devices (e.g., thecomputing device 116, the image processor unit 151, and/or the x-raycontroller 110 of FIG. 1).

At 5102, the method 5100 includes receiving a request to commenceimaging with the stationary CT imaging system. For example, an operatormay input a command or otherwise indicate to the computing system that adiagnostic scan will be performed. Further, a subject (such as apatient) may be prepared for the diagnostic scan. One or more anatomiesof the subject (such as body parts or systems including brain, heart,respiratory system, etc.) may be identified to be a region of interest(ROI) to be scanned. The subject (such as the subject 127 of FIG. 1) maybe positioned on a support surface (such as the support surface 135 ofFIG. 1). In some examples, a support surface motor controller (e.g., thesupport surface motor controller 126 of FIG. 1) may move the supportsurface so that a desired anatomy of the subject is within an imagingfield of view. In other examples, an imaging unit of the stationary CTimaging system may be moved with respect to the subject, such as themotor controller 112 of FIG. 1.

At 5104, the method 5100 includes performing a scout scan. The scoutscan provides a projection view along a longitudinal axis of the imagingsubject and generally provides aggregations including internalstructures of the subject. A scout scan may be used to image the ROI ofthe subject for the subsequent diagnostic scan. The scout scan may be anultra-low dose CT scan, a tomosynthesis scan, or one or more traditionalscout scans.

At 5106, the method 5100 includes obtaining imaging parameters. Forexample, the operator may input or select the imaging parametersaccording to a scanning protocol or a menu. The imaging parameters mayinclude setting a scan timing, a starting location, an ending location,etc. As one example, the scan timing may include a start time and aduration for imaging each section. As another example, the imagingparameters may include a total radiation dose to be delivered to thesubject, whether multi-energy imaging or single energy imaging isdesired, a type of x-ray blocking, modulation, or filtering that will beperformed (if any), etc.

At 5108, the method 5100 includes generating a scan prescription basedon the scout scan and the imaging parameters. As an example, a series ofdiagnostic scans may be carried out for a desired anatomy or ROI, andthe scan prescription may determine a number of views to obtain at eachscan location, an energy for operating each x-ray source and/or emitter,slice thickness, helical pitch (e.g., when the CT system is an uprightsystem as explained above with respect to FIG. 4), etc.

At 5110, the method 5100 includes determining if multi-energy imaging isrequested. Multi-energy imaging enables the interrogation of materialsthat have different attenuation properties at different energies andproduces more image types than single energy imaging. For example,multi-energy imaging may produce weighted average images that aresimilar to single energy spectra, monochromatic (e.g., monoenergetic)images of attenuation at a single photon energy rather than a spectrum,basis material images, and/or electron density maps. As an illustrativeexample, the multi-energy imaging may enable bone to be removed fromvascular scans so that vascular structures and pathologies may be moreeasily identified.

If multi-energy imaging is not requested, the method 5100 proceeds to5112 and includes performing a single energy scan, as will be describedbelow with respect to FIG. 52. For example, each x-ray source of thestationary CT imaging system may be operated at a same energy.

At 5114, the method 5100 includes reconstructing imaging from projectiondata, as will be described below the respect to FIG. 53. For example,x-ray detectors (e.g., of the detector array 147 of FIG. 1) may measureattenuated x-rays emitted by the x-ray sources after they pass throughthe subject, and an image reconstructor (e.g., the image reconstructor130 of FIG. 1) may use one or a combination of different reconstructiontechniques to correct or compensate for scatter, motion, and/or thesparse views afforded by the stationary CT imaging system.

At 5120, the method 5100 includes displaying and/or saving thereconstructed images. For example, the reconstructed images may bedisplayed on a display device, such as the display device 132 of FIG. 1,in addition to being saved to a memory (e.g., the mass storage 118and/or the PACS 124 of FIG. 1). In other examples, the reconstructedimages may be saved and accessed at a later time for display. In someexamples, the operator may interact with or annotate the reconstructedimages, and the annotations may also be saved, such as a separate imagefile. The method 5100 may then end.

Returning to 5110, if multi-energy imaging is requested, the method 5100proceeds to 5116 and includes performing the multi-energy scan, as willbe elaborated with respect to FIG. 54. For example, the x-ray sourcesmay be operated at different energies or may be switched betweendifferent energies throughout the scan.

At 5118, the method 5100 includes reconstructing multi-energy imagesfrom the projection data, as will be elaborated below with respect toFIG. 55. Similar to the single energy reconstruction, the imagereconstructor may use one or a combination of different reconstructiontechniques to correct or compensate for scatter, motion, and/or sparseviews and may additionally separately reconstruct high energy images andlow energy images, at least in some examples. For example, the highenergy images and the low energy images may be blended for a finaldiagnostic image.

Continuing to FIG. 52, a flow chart of a method 5200 for performing asingle energy scan is shown. For example, the method 5200 may beperformed as a part of the method 5100 of FIG. 51 (e.g., at 5112).

At 5202, the method 5200 includes activating stationary x-ray sources.The stationary x-ray sources may be included in one or more distributedx-ray source units (e.g., the distributed x-ray source unit 104 ofFIG. 1) and may include a plurality of focal spots from which beams ofx-ray radiation are emitted. In order to image a relatively large fieldof view of the subject, the stationary x-ray sources may be arranged inany of the configurations described with respect to FIGS. 25-30, forexample.

In some examples, activating the stationary x-ray sources includesactivating the x-ray sources simultaneously or in an alternatingfashion, as optionally indicated at 5204. By energizing the x-raysources simultaneously or in an alternating fashion, “virtual rotation”of the x-ray source is achieved to generate a sinogram of x-rayprojection data. For example, a first x-ray source (e.g., a firstemitter) may be energized at a first time, and a second x-ray sourcethat is adjacent to the first x-ray source may be energized at a secondtime, after the first time, etc., until all of the x-ray sources havebeen energized in sequence. As another example, a first portion of thex-ray sources may be energized at the first time, a second portion ofthe x-ray sources may be energized at the second time, etc. Whenmultiple x-ray sources are activated simultaneously, the x-ray sourcesthat are activated simultaneously may be spaced apart from one anothersuch that x-ray energy from two emitters do not coincide on the samedetector elements.

In some examples, activating the stationary x-ray sources additionallyor alternatively includes activating the x-ray sources according to atime-sequential sampling pattern, as optionally indicated at 5206. Forexample, the time-sequential sampling pattern may ensure that there isonly one projection acquired at any time instant. As such, theprojection data may be acquired in angular (e.g., a sampling range ofview angles) and temporal space. For example, the time-sequentialsampling pattern may specify the angular position of the view to collectat any given time to maximize the temporal inter-projection intervalwhile reducing or eliminating motion artifacts. In some examples,multiple sources may be activated simultaneously during thetime-sequential sampling pattern. For example, a first emitter from eachx-ray source unit may activated simultaneously, followed by a secondemitter from each x-ray source unit, then a third emitter from eachx-ray source, etc. Alternatively, a first set of emitters (e.g., spacedapart by equidistant amounts) may be activated simultaneously, then asecond set of emitters (also spaced apart by equidistant amounts) may beactivated, etc.

In some examples, activating the stationary x-ray sources additionallyor alternatively includes activating the x-ray sources with varying fanbeams, as optionally indicated at 5208. For example, different focalspots may emit partial fan beams of different relative angular ranges toprovide relatively complete coverage of the field of view, such asdescribed with respect to FIGS. 42A and 42B. As another example, anx-ray beam may be split into a plurality of narrow fan beams throughcollimation, such as described with respect to FIG. 44. In someexamples, narrow fan beam measurements may be alternated with wide beammeasurements from the same x-ray source.

In some examples, activating the stationary x-ray sources additionallyor alternatively includes activating a subset of the x-ray sources at alow dose with collimation for scatter measurements, as optionallyindicated at 5210. As one example, the collimation may be achievedthrough an adjustable pre-subject collimator, such as described withrespect to FIG. 43. The collimation may reduce a fan angle of the x-raybeam emitted by each x-ray source, for example. Further, the fan angleof the x-ray beam may be adjusted so that the x-ray beam is directed toa portion of the detector, enabling a remaining portion of the detectorto measure scatter, such as described with respect to FIG. 45.

In some examples, activating the stationary x-ray sources additionallyor alternatively includes modulating a subset of the x-ray sources forscatter measurement, as optionally indicated at 5212. For example, amodulator may be positioned in front of one or more of the x-raysources, and the x-ray beam emitted by the one or more x-ray sources maypass through the modulator. As described with respect to FIG. 47, themodulator may comprise a spatially variant x-ray attenuating material sothat low energy photons are selectively filtered out of portions of thex-ray beam in a known geometric pattern.

At 5214, the method 5200 includes receiving attenuated x-rays atdetectors. For example, the detectors may include detector cells of asame or varying size and of a same or different detector type, such asdescribed with respect to FIGS. 40 and 41. The detectors may bephoton-counting, scintillation-based, or a combination of the two, forexample.

In some examples, receiving the attenuated x-rays at the detectorsincludes rotating the detectors, as optionally indicated at 5216. Forexample, certain embodiments may include a smaller angular coveragedetector array that rotates with respect to the subject and with respectto the stationary x-ray sources, such as described with respect to FIGS.30 and 36. As such, the detector array may be rotated about a centralaxis in order to measure different view angles.

In some examples, receiving the attenuated x-rays at the detectorsadditionally or alternatively includes sampling the detectors outside ofthe primary beam for scatter measurements, as optionally indicated at5218. As particularly described with respect to FIG. 45 and FIGS. 48-49,a portion of the detector array that is outside of the primary x-raybeam may be used to detect scattered radiation, and the scattermeasurements may be processed with analytic, Monte Carlo, and/or deeplearning scatter estimation/correction algorithms.

In some examples, receiving the attenuated x-rays at the detectorsadditionally or alternatively includes correcting the detector outputbased on the scatter measurements or estimations, as optionallyindicated at 5220. As one example, a deep learning scatter estimationalgorithm may use both the primary and scatter transmission profiles, acorresponding attenuation profile, and adjacent scatter measurements asinputs and may output an estimated scatter profile. Similarly, a deeplearning scatter correction algorithm may use both the primary andscatter transmission profiles, the corresponding attenuation profile,and the adjacent scatter measurements as inputs and may output anestimate of a scatter-corrected primary profile. Such deep learningnetworks use ground truth data for training, which may includescatter-corrupted data (e.g., using full fan-beams such that amaximum/typical amount of scatter is present) and scatter-reduced data(e.g., using partial fan-beams so that less scatter is present). Theprimary and scatter transmission profiles may also be referred to as atotal transmission profile, and may be generated from detector outputfrom each detector element of the plurality of detector elements(including detector elements that intercept a primary x-ray beam anddetector elements that do not intercept the primary x-ray beam). Theattenuation profile may be generated from output from only the subset ofdetector elements that intercept the primary x-ray beam, and the scattermeasurement may be generated from output from only one or more detectorelements of the plurality of detector elements outside the primary x-raybeam. Further, because narrow beams produce less scatter, narrow beamprojections may be subtracted from wide beam projections having morescatter, such as those obtained from measuring full x-ray beams, toobtain an estimate of the scatter from portions outside of the narrowx-ray beam, such as mentioned above with respect to FIG. 43.Additionally, scatter may be estimated or measured at one view or asubset of views and the scatter estimation may be applied to remainingviews via interpolation.

At 5222, the method 5200 includes determining if all views are obtained.For example, each view may refer to x-ray radiation attenuationmeasurements (e.g., projection data) acquired by a given detector andassociated with a given beam of x-ray radiation intercepted by thedetector at a given angle. It may be determined that all views areobtained when all of the views in the prescription generated at 5108 ofFIG. 51 are obtained. If all of the views are not obtained, the method5200 returns to 5202 and includes continuing to activate the stationaryx-ray sources. In contrast, if all of the views are obtained, the method5200 proceeds to 5224 and includes determining if the ROI has beenimaged. If the ROI has been imaged, the method 5200 ends. If the ROI hasnot been imaged, the method 5200 proceeds to 5226 and includes movingthe patient or gantry (e.g., the imaging unit supporting the x-raysources and detector arrays) to a next position so that additional viewsmay be obtained at the next position (e.g., by activating the stationaryx-ray sources at 5202). In some examples, such as in the uprightconfiguration explained above with respect to FIG. 4, the gantry/imagingunit may be translated vertically with respect to ground (e.g., up ordown) along a patient axis (e.g., the longitudinal axis of the patient)during imaging (e.g., while the x-ray sources are activated) at a speedthat may be based on the selected helical pitch.

Next, FIG. 53 shows a flow chart of a method 5300 for reconstructingimages based on measurements during a single energy scan. For example,the method 5300 may be performed as a part of the method 5100 of FIG. 51(e.g., at 5114).

At 5302, the method 5300 includes obtaining projection data from thesingle energy scan, such as the single energy scan described above withrespect to FIG. 52.

At 5304, the method 5300 includes determining if motion compensation isdesired. For example, motion artifacts may be introduced throughrespiratory and cardiac motion during the single energy scan. As oneexample, motion compensation may be desired during chest imaging.

If motion compensation is not desired, the method 5300 proceeds to 5306and includes reconstructing the images using a selected technique. Insome examples, the selected technique includes entering projection datainto a generative adversarial network (GAN), as optionally indicated at5308. For example, the GAN may be a deep learning network that is usedto generate densely sampled sinograms and includes a discriminator thatoperates in the reconstructed image domain. The discriminator estimateswhether the reconstructed image was generated from a realdensely-sampled dataset versus from a real sparsely-sampled viewdataset. The projection data that is entered into the GAN may be asparse view projection dataset (e.g., having a reduced number of viewsthan those typically obtained with conventional CT imaging systems, suchas 100 views rather than 1000 views). The sparse view projection datasetmay be entered as input to the generator of the GAN, which may output adense-view dataset (e.g., filling in the missing views), where thegenerator is trained to output the dense-view dataset by thediscriminator. The dense-view dataset may be reconstructed to form areconstructed image using a suitable reconstruction technique such asfiltered backprojection.

Turning briefly to FIG. 56, an example GAN 5600 is shown. In the GAN5600, a real sparse-view dataset 5602 is input into a generator 5604,which generates an artificial (e.g., estimated) dense-view dataset 5606from the real sparse-view dataset 5602. The artificial dense-viewdataset 5606 undergoes a filtered back projection 5608 to produce afirst reconstructed image 5610. The generator may be a suitable network,such as a deconvolutional neural network. To train the generator, areconstructed image produced by the generator (e.g., the firstreconstructed image 5610) may be entered into a discriminator along witha second reconstructed image 5616 that is generated from a realdense-view dataset 5612 via a filtered back projection 5614. Thediscriminator attempts to determine which image is “real” and whichimage is “fake” (e.g., generated from an artificial sparse view datasetrather than a real dense view dataset). The generator is trained usingfeedback from the discriminator, as the generator aims to fool thediscriminator. Further, in some examples, both the artificial dense-viewdataset 5606 and the real dense-view dataset 5612 are input into astandard loss function 5618, as indicated by dashed arrows. The standardloss function 5618 may compare the artificial dense-view dataset 5606 tothe real dense-view dataset 5612 and output from the standard lossfunction may be used to train the generator. In some examples, thestandard loss function 5618 may additionally or alternatively comparethe corresponding reconstructions, as indicated by dotted arrows. Thefirst reconstructed image 5610 and the second reconstructed image 5616are also input into a discriminator loss function 5620, as indicated bysolid arrows and as described above. While FIG. 56 shows a real sparseview dataset being used to train the generator, it is to be understoodthat the sparse view dataset(s) used to train the generator may bepseudo sparse view datasets generated from real dense view datasets. Forexample, a projection dataset obtained by a conventional CT imagingsystem having a large number of views (e.g., 1000), a large view anglerange (e.g., greater than 180 degrees), and a large FOV (e.g., 50 cm)may be modified to generate the pseudo sparse view dataset by discardingviews in order to match the view number, view angle range, and FOV ofthe projection data obtained by the stationary CT imaging system.

Returning to 5306 of FIG. 53, in some examples, the selected techniqueadditionally or alternatively includes applying iterative reconstructionwith deep learning, as optionally indicated at 5310. The iterativereconstruction with deep learning may include an unrolled (e.g.,unfolded) iterative reconstruction where one or more priors of theiterative reconstruction are learned from one or more deep learningnetworks. The deep learning may be trained to recover good qualityimages from sparse-view datasets. Each update stage combines a datafitupdate step and a deep learning update step (in parallel or insequence). The deep learning networks are trained such that the finalimage estimate has good image quality or looks similar to the imageproduced from a densely sampled dataset.

Turning briefly to FIG. 57, an example unrolled iterative reconstructionnetwork 5700 is shown. In the unrolled iterative reconstruction network5700, a sparse-view data set 5702 is input into a first datafit updatestep 5706, which also receives an initial image estimate 5704. Theinitial image estimate is also received by a first deep learning updatestep 5708 that is in parallel with the first datafit update step 5706.The output of the first datafit update step 5706 and the output of thefirst deep learning update step 5708 produce a first image estimateiteration 5710, which is put into each of a second datafit update step5712 and a second deep learning update step 5714 in parallel. The seconddatafit update step 5712 also receives the sparse-view data set 5702 andcompares the sparse-view data set 5702 to the first image estimateiteration 5710 to determine a measurement error. The output of thesecond datafit update step 5712 and the output of the second deeplearning update step 5714 produce a second image estimate iteration5716, which is put into each of a third datafit update step 5718 and athird deep learning update step 5720 in parallel. The third datafitupdate step 5718 also receives the sparse-view data set 5702 andcompares the sparse-view data set 5702 to the second image estimateiteration 5716 to determine a measurement error. The output of the thirddatafit update step 5718 and the output of the third deep learningupdate step 5720 produce a third image estimate iteration 5722. Thethird image estimate iteration 5722 is input into a loss function 5726along with an image from dense views 5724. The measurement errorfeedback at each datafit update step may help recover structuralsubtleties in the reconstructed image and suppress inconsistencies andinstabilities induced by the deep learning methods used in each deeplearning update step.

In some examples, the iterative reconstruction strategy synergizes deeplearning, analytic mapping, iterative refinement, and compressed sensingas an analytic, compressive, iterative deep (ACID) network.Reconstructing an image with the ACID network may include entering thesparse view projection dataset into a deep learning network trained tooutput a first initial reconstructed image, and regularizing the firstinitial reconstructed image using compressed sensing to generate asecond initial reconstructed image. For example, via compressed sensing,the first initial reconstructed image may be transformed to the spatialdomain via a Fourier transform and nonzero coefficients may be inferred,which may be used to generate the second initial reconstructed image viaan inverse Fourier transform. The sparse view projection dataset maythen be updated based on an analytic mapping between the first initialimage and the second initial image. The updated sparse view projectiondataset may be entered into the deep learning network to generate athird initial reconstructed image, which may be iteratively refinedbased on the second initial reconstructed image to form a finalreconstructed image. In some examples, multiple rounds of updating ofthe sparse view projection dataset may be performed before the finalimage is output.

Returning to 5306 of FIG. 53, in some examples, the selected techniqueadditionally or alternatively includes applying a stackedreconstruction, as optionally indicated at 5312. The stackedreconstruction may be performed by back projecting each single view ontoa separate image and using these single-view back projections as inputto a deep learning network, also referred to as stacked back projection.Optionally, a filter may be applied to each view prior to backprojection. In some examples, the reconstruction may be performed usingan analytical inverse of a forward transform.

In some examples, the selected technique additionally or alternativelyincludes applying hierarchical reconstruction, as optionally indicatedat 5314. For example, the hierarchical reconstruction approach may beused to reconstruct non-uniformly sampled view datasets. In a firststage(s) of the reconstruction, each set of locally densely sampledviews is used to generate a respective single view with partial(weighted) line integrals for each x-ray source. For example, referringto FIG. 50, the set of views 5006 a may be used to generate a firstsingle view, the set of views 5006 b may be used to generate a secondsingle view, etc. This first stage is a tomosynthesis-likereconstruction and may be achieved using a deep learning network. Thefirst stage may also use the stacked back projection approach describedabove. In a second stage, the single views with partial line integralsare used to generate reconstructed images. This second stage is atime-of-flight-like reconstruction and may be achieved using sparseiterative reconstruction or using a deep learning network. The first orsecond stage may also use the analytic inverse approach described above.In this way, the sparse view projection dataset may be partitioned intoa plurality of densely-sampled view sets, each densely-sampled view setmay be entered into a network trained to output a respective single viewfor each densely-sampled view set, and a final image may bereconstructed from all the single views.

In some examples, the selected technique additionally or alternativelyincludes extrapolating missing views, as optionally indicated at 5316.For example, in some stationary CT imaging system architectures, theavailable view range is less than a 180 degree (or more) fan angletypically used in CT imaging. For example, the x-ray source may extendover 160 degrees, and the x-ray detector may extend over 200 degrees. Insuch examples, deep learning may be used to extrapolate the missingviews in the view angle direction. Training data may be generated byusing complete data and deleting the missing data in the input data. Inanother example, a deep learning reconstruction approach similar to theones listed for the sparse view scenarios above may be used. Further, ifthe final reconstructed image volumes still have better spatialresolution in one direction (e.g., in coronal planes) than in the otherdirection (e.g., in the sagittal planes), such datasets may be primarilyshown to the view as coronal images.

In some examples, the selected technique additionally or alternativelyincludes separately reconstructing large focal spot views and smallfocal spot views and combining the images, as optionally indicated at5318. As described with respect to FIGS. 40 and 41, for example, thelarge focal spots may provide a better signal-to-noise ratio, and thesmall focal spots may provide better spatial resolution. The large focalspot views may be reconstructed into a first image having lowsignal-to-noise, and the small focal spot views may be reconstructedinto a second image having high spatial resolution. The resulting lownoise and high resolution images may be combined using a deep learningnetwork so that the low noise qualities from the large focal spot viewsand the high resolution qualities from the small focal spot views arekept in the combined image. The method 5300 may then end.

Returning to 5304, if instead motion compensation is desired, the method5300 proceeds to 5320 and includes reconstructing the images using aselected technique with motion compensation. In some examples, theselected technique with motion compensation includes extrapolatingmissing views, as optionally indicated at 5322. For example, a sparsedataset may be acquired in order to reduce the overall scan time,thereby reducing motion, and missing views may be extrapolated, such asdescribed above at 5316.

In some examples, the selected technique with motion compensationadditionally or alternatively includes applying spatio-temporalfiltering and performing the reconstruction, as optionally indicated at5324. For example, filtering may be applied in the time direction, suchas using a finite impulse response filter, and also in the angulardirection, such as using a discrete Fourier transform. The filteredprojections may be back-projected to obtain a reconstructed image of thesubject.

In some examples, the selected technique with motion compensationadditionally or alternatively includes time-resolving views,reconstructing view sets, and applying motion correction, as optionallyindicated at 5326. For example, the total set of views may bepartitioned into several sparser but more time-resolved subsets ofviews. The time-resolved subsets may include views taken at the same orclose to the same time. As an example, if multiple emitters areactivated simultaneously, each view obtained from those emittersactivated simultaneously may form a subset of views. Each subset ofviews may be reconstructed separately using a selected sparse viewreconstruction technique, such as described above at 5306. Motionestimation can be performed based on the time-resolved reconstructions.Then, based on the motion estimation, motion correction can be appliedto reconstruct the complete set of views into one time-resolvedreconstruction or to warp and recombine all subset reconstructions. Themethod 5300 may then end.

Thus, FIGS. 52 and 53 provide for generating a sparse view projectiondataset by activating a plurality of emitters of one or more stationarydistributed x-ray source units to emit x-ray beams toward an objectwithin an imaging volume, where the x-ray source unit(s) does not rotatearound the imaging volume, and receiving attenuated x-ray beams with oneor more detector arrays. As described above, the sparse view projectiondataset differs from conventional dense view projection datasets in oneor more of a total number of views, a spacing of views, a view anglerange, and a field of view. An image may be reconstructed from thesparse view projection dataset using a sparse view reconstruction methodthat includes a deep learning network. The deep learning network may betrained with training data that includes: a dense view projectiondataset and/or one or more training images generated from the dense viewprojection dataset, and a pseudo sparse view projection datasetgenerated from the dense view projection dataset and/or one moretraining images generated from the pseudo sparse view projectiondataset. The pseudo sparse view projection dataset may be generated bydiscarding a plurality of views of the dense view projection dataset sothat a total number of views, a spacing of views, a view angle range,and a field of view of the pseudo sparse view dataset matches the totalnumber of views, the spacing of views, the view angle range, and thefield of view of the sparse view projection dataset. In this way, thetraining data that is used to train the deep learning network may matchthe projection data obtained by the stationary CT system at least interms of the number and spacing of views, which may enable the trainednetwork to more accurately aid in high-quality image reconstructionusing sparse view datasets. As used herein, a deep learning network mayrefer to a convolutional neural network, an artificial neural network, arecurrent neural network, and/or other suitable multi-layered networksor machine learning algorithms.

Continuing to FIG. 54, a flow chart of a method 5400 for performing amulti-energy scan is shown. For example, the method 5400 may beperformed as a part of the method 5100 of FIG. 51 (e.g., at 5116).

At 5402, the method 5400 includes activating stationary x-ray sources(e.g., emitters) to emit two or more energies. In some examples,activating the stationary x-ray sources to emit the two or more energiesincludes activating the x-ray sources simultaneously or in analternating fashion, as optionally indicated at 5404.

In some examples, activating the stationary x-ray sources to emit thetwo or more energies additionally or alternatively includes activatingthe x-ray sources arranged with fixed, alternating voltages, asoptionally indicated at 5406. For example, a first segment or portion ofthe stationary x-ray sources may be operated at a higher voltage to emithigher energy x-ray beams, and a second segment or portion of thestationary x-ray sources may be operated at a lower voltage to emitlower energy x-ray beams. Examples of such configurations are describedwith respect to FIGS. 31-37.

In some examples, activating the stationary x-ray sources to emit thetwo or more energies additionally or alternatively includes switchingthe x-ray source voltage, as optionally indicated at 5408. For example,as described with respect to FIGS. 1 and 39A-39B, a voltage switcher mayadjust the stationary x-ray sources between different energizationmodes, such as a lower energy mode and a higher energy mode.

In some examples, activating the stationary x-ray sources to emit thetwo or more energies additionally or alternatively includes applyingfilters to separate different energies, as optionally indicated at 5410.For example, as described with respect to FIGS. 38A and 38B, a filtermay be selectively applied to the x-ray sources emitting a first (e.g.,lower) energy x-ray beam and not to the x-ray sources emitting a second(e.g., higher) energy x-ray beams.

Further, it may be understood that collimation, modulation, and varyingfan beams may be used when activating the stationary x-ray sources toemit the two or more energies, similar to that described above withrespect to FIG. 52.

At 5412, the method 5400 includes receiving attenuated x-rays atdetectors, similar to that described above at 5214 of FIG. 52. In someexamples, receiving the attenuated x-rays at the detectors includes thedetectors being energy-discriminating, energy-integrating, or hybriddetectors, as optionally indicated at 5414. As described with respect toFIGS. 40 and 41, the different detectors may have differing sensitivityor differing spatial resolution, for example. When energy-discriminatingdetectors are used, all the x-ray sources may be operated at the samepeak voltage and different x-ray spectra may be obtained by thedifferent energy-discriminating detectors.

In some examples, receiving the attenuated x-rays at the detectorsadditionally or alternatively includes rotating the detectors, asoptionally indicated at 5416, in the manner described above with respectto 5216 of FIG. 52. Further, it may be understood that scattermeasurements or estimations may be performed and used to correct thedetector output, such as described with respect to FIG. 52.

At 5418, the method 5400 includes determining if all views are obtained.For example, each view may refer to x-ray radiation attenuationmeasurements (e.g., projection data) acquired by a given detector andassociated with a given beam of x-ray radiation intercepted by thedetector at a given angle. It may be determined that all views areobtained when all of the views in the prescription generated at 5108 ofFIG. 51 are obtained. If all of the views are not obtained, the method5400 returns to 5402 and includes continuing to activate the stationaryx-ray sources to emit the two or more energies. In contrast, if all ofthe views are obtained, the method 5400 proceeds to 5420 and includesdetermining if a ROI has been imaged. If the ROI has been imaged, themethod 5400 ends. If the ROI has not been imaged, the method 5400proceeds to 5422 and includes moving the patient or gantry to a nextposition so that additional views may be obtained at the next position(e.g., by activating the stationary x-ray sources to emit the two ormore energies at 5402), such as mentioned above with respect to FIG. 52.

Next, FIG. 55 shows a flow chart of a method 5500 for reconstructingimages based on measurements during a single energy scan. For example,the method 5500 may be performed as a part of the method 5100 of FIG. 51(e.g., at 5118).

At 5502, the method 5500 includes obtaining projection data from themulti-energy scan, such as the multi-energy scan described above withrespect to FIG. 54.

At 5504, the method 5500 includes reconstructing the projection data. Insome examples, reconstructing the projection data includesreconstructing high-energy and low-energy images separately using aselected technique, as optionally indicated at 5506. Various techniquesthat may be selected are described with respect to FIG. 53 (at 5306) forreconstructing projection data from single energy scans. In someexamples, various sparse view reconstruction techniques may be used.

The separate high-energy and low-energy images may be processed byapplying image domain decomposition to obtain basis material images ormonochromatic images, as optionally indicated at 5508. In some examples,reconstructing the projection data additionally or alternativelyincludes entering adjacent views at each energy into a deep learningnetwork/model trained to output basis material projections ormonochromatic projections for each view, as optionally indicated at5510. For example, a first view at a first energy may input into thedeep learning model along with a second, adjacent view (or, when fastvoltage switching is used, the same view) at a second energy, and thedeep learning model may output a joint view (e.g., a joint projection)as a basis material view or monochromatic view. In some examples,reconstructing the projection data additionally or alternativelyincludes reconstructing basis material images or monochromatic imagesfrom the projections, as optionally indicated at 5512. For example, adeep learning network may use a number of adjacent views at high and lowenergy as input and may output one or more views at specific view anglesthat represent either basis material projections or monochromatic basisprojections. Image-domain decomposition then may be performed to obtainbasis materials images or monochromatic images. The method 5500 may thenend.

FIGS. 2-7 and 9-21 show example configurations with relative positioningof the various components. If shown directly contacting each other, ordirectly coupled, then such elements may be referred to as directlycontacting or directly coupled, respectively, at least in one example.Similarly, elements shown contiguous or adjacent to one another may becontiguous or adjacent to each other, respectively, at least in oneexample. As an example, components laying in face-sharing contact witheach other may be referred to as in face-sharing contact. As anotherexample, elements positioned apart from each other with only a spacethere-between and no other components may be referred to as such, in atleast one example. As yet another example, elements shown above/belowone another, at opposite sides to one another, or to the left/right ofone another may be referred to as such, relative to one another.Further, as shown in the figures, a topmost element or point of elementmay be referred to as a “top” of the component and a bottommost elementor point of the element may be referred to as a “bottom” of thecomponent, in at least one example. As used herein, top/bottom,upper/lower, above/below, may be relative to a vertical axis of thefigures and used to describe positioning of elements of the figuresrelative to one another. As such, elements shown above other elementsare positioned vertically above the other elements, in one example. Asyet another example, shapes of the elements depicted within the figuresmay be referred to as having those shapes (e.g., such as being circular,straight, planar, curved, rounded, chamfered, angled, or the like).Further, elements shown intersecting one another may be referred to asintersecting elements or intersecting one another, in at least oneexample. Further still, an element shown within another element or shownoutside of another element may be referred as such, in one example.

As used herein, the term “approximately” is construed to mean plus orminus five percent of the range unless otherwise specified.

In one embodiment, a modular imaging system comprises: a plurality ofdistributed x-ray source units releasably coupled to a plurality ofdetector arrays, with the plurality of distributed x-ray source unitsand the plurality of detector arrays forming a self-supporting structureincluding a central opening shaped to receive a subject to be imaged. Ina first example of the modular imaging system, each distributed x-raysource unit of the plurality of distributed x-ray source units isinterchangeable with each other distributed x-ray source unit of theplurality of distributed x-ray source units and each detector array ofthe plurality of detector arrays is interchangeable with each otherdetector array of the plurality of detector arrays without altering animaging quality of the modular imaging system. A second example of themodular imaging system optionally includes the first embodiment, andfurther includes wherein a central axis of the central opening extendsparallel with a ground surface on which the self-supporting structuresits. A third example of the modular imaging system optionally includesone or both of the first and second embodiments, and further includeswherein a length from the central axis to each distributed x-ray sourceunit of the plurality of distributed x-ray source units is equal to alength from the central axis to each detector array of the plurality ofdetector arrays. A fourth example of the modular imaging systemoptionally includes one or more or each of the first through thirdexamples, and further includes wherein the plurality of distributedx-ray source units consists of an odd number of distributed x-ray sourceunits and the plurality of detector arrays consists of an odd number ofdetector arrays. A fifth example of the modular imaging systemoptionally includes one or more or each of the first through fourthexamples, and further includes wherein the plurality of distributedx-ray source units includes exactly three distributed x-ray source unitscomprising a first distributed x-ray source unit, a second distributedx-ray source unit, and a third distributed x-ray source unit, and theplurality of detector arrays includes exactly three detector arrayscomprising a first detector array, a second detector array, and a thirddetector array. A sixth example of the modular imaging system optionallyincludes one or more or each of the first through fifth examples, andfurther includes wherein a first axis extending along a centerline ofthe first distributed x-ray source unit is parallel with a second axisextending along a centerline of the first detector array, a third axisextending along a centerline of the second distributed x-ray source unitis parallel with fourth axis extending along a centerline of the seconddetector array, and a fifth axis extending along a centerline of thethird distributed x-ray source unit is parallel with a sixth axisextending along a centerline of the third detector array. A seventhexample of the modular imaging system optionally includes one or more oreach of the first through sixth examples, and further includes whereineach distributed x-ray source unit of the plurality of distributed x-raysource units is arranged between two adjacent detector arrays of theplurality of detector arrays. An eighth example of the modular imagingsystem optionally includes one or more or each of the first throughseventh examples, and further includes wherein each distributed x-raysource unit of the plurality of distributed x-ray source units isarranged in an alternating configuration with each detector array of theplurality of detector arrays. A ninth example of the modular imagingsystem optionally includes one or more or each of the first througheighth examples, and further includes wherein the self-supportingstructure has a hexagonal profile. A tenth example of the modularimaging system optionally includes one or more or each of the firstthrough ninth examples, and further includes wherein a length along acenterline of each distributed x-ray source unit of the plurality ofdistributed x-ray source units is equal to a length along a centerlineof each detector array of the plurality of detector arrays. An eleventhexample of the modular imaging system optionally includes one or more oreach of the first through tenth examples, and further includes whereineach distributed x-ray source unit of the plurality of distributed x-raysource units is fixedly coupled to an adjacent detector array of theplurality of detector arrays via a respective bracket.

In one embodiment, a portable imaging system comprises: a firstdistributed x-ray source unit, a second distributed x-ray source unit,and a third distributed x-ray source unit; a first detector arrayarranged directly opposite to the first distributed x-ray source unitacross a central axis of the portable imaging system and releaseablycoupled to the second distributed x-ray source unit and the thirddistributed x-ray source unit; a second detector array arranged directlyopposite to the second distributed x-ray source unit across the centralaxis and releaseably coupled to the first distributed x-ray source unitand the third distributed x-ray source unit; and a third detector arrayarranged directly opposite to the third distributed x-ray source unitacross the central axis and releasably coupled to the first distributedx-ray source unit and the second distributed x-ray source unit. In afirst example of the portable imaging system, the first detector arrayreleasably couples to the second distributed x-ray source unit and thethird distributed x-ray source unit at a first angle relative to thesecond detector array and the third detector array, and the seconddetector array releasably couples to the first distributed x-ray sourceunit and the third distributed x-ray source unit at a second anglerelative to the third detector array. A second example of the portableimaging system optionally includes the first example, and furtherincludes wherein the first angle is equal to the second angle. A thirdexample of the portable imaging system optionally includes one or bothof the first and second examples, and further includes wherein the firstdistributed x-ray source unit, the second distributed x-ray source unit,the third distributed x-ray source unit, the first detector array, thesecond detector array, and the third detector array are each verticallyfixed within a same imaging plane relative to a ground surface on whichthe portable imaging system sits. A fourth example of the portableimaging system optionally includes one or more or each of the firstthrough third examples, and further includes wherein the firstdistributed x-ray source unit, the second distributed x-ray source unit,the third distributed x-ray source unit, the second detector array, andthe third detector array are each supported by the first detector arrayin a vertical direction relative to a ground surface on which theportable imaging system sits.

In one embodiment, a method comprises: acquiring a scan of a subject viaa modular imaging system by: energizing a first distributed x-ray sourceunit to emit x-ray radiation in a first direction and intercepting thex-ray radiation at a first detector array arranged opposite to the firstdistributed x-ray source unit; energizing a second distributed x-raysource unit to emit x-ray radiation in a second direction andintercepting the x-ray radiation at a second detector array arrangedopposite to the second distributed x-ray source unit; and energizing athird distributed x-ray source unit to emit x-ray radiation in a thirddirection and intercepting the x-ray radiation at a third detector arrayarranged opposite to the third distributed x-ray source unit. In a firstexample of the method, the method further includes releasably couplingthe first distributed x-ray source unit to the second detector array andthe third detector array, releasably coupling the second distributedx-ray source unit to the first detector array and the third detectorarray, and releasably coupling the third distributed x-ray source unitto the first detector array and the second detector array. A secondexample of the method optionally includes the first example, and furtherincludes: while acquiring the scan of the subject, maintaining the firstdistributed x-ray source unit vertically above the third detector arrayrelative to a ground surface on which the modular imaging system sitsthroughout an entirety of the scan, maintaining the second distributedx-ray source unit vertically below the third detector array throughoutthe entirety of the scan, and maintaining the third distributed x-raysource unit vertically below the second detector array throughout theentirety of the scan. A third example of the method optionally includesone or both of the first and second examples, and further includeswherein energizing the first distributed x-ray source unit includesproviding electrical energy to the first distributed x-ray source unitvia a portable battery unit, energizing the second distributed x-raysource unit includes providing electrical energy to the seconddistributed x-ray source unit via the portable battery unit, andenergizing the third distributed x-ray source unit includes providingelectrical energy to the third distributed x-ray source unit via theportable battery unit.

The disclosure also provides support for an imaging system, comprising:a chamber shaped to enclose a subject to be imaged, a support surfacedisposed within the chamber and shaped to maintain the subject in anupright position, and an annular imaging unit encircling the chamber andhaving a fixed angular orientation to the chamber, the annular imagingunit including a distributed x-ray source unit and a detector arrayarranged opposite to each other across the chamber. In a first exampleof the system, the distributed x-ray source unit and the detector arrayare arranged along an inner perimeter of the annular imaging unit. In asecond example of the system, optionally including the first example,the distributed x-ray source unit includes a plurality of x-ray emittersarranged along the inner perimeter and configured to emit x-rayradiation toward a plurality of detectors of the detector array. In athird example of the system, optionally including one or both of thefirst and second examples, the plurality of x-ray emitters spans anangular range of at least 150 degrees around the inner perimeter. In afourth example of the system, optionally including one or more or eachof the first through third examples, the detector array includes aplurality of x-ray detectors arranged along the inner perimeter, andwherein the plurality of x-ray detectors spans an angular range of atleast 180 degrees around the inner perimeter. In a fifth example of thesystem, optionally including one or more or each of the first throughfourth examples, the detector array is configured to rotate relative tothe distributed x-ray source unit. In a sixth example of the system,optionally including one or more or each of the first through fifthexamples, the annular imaging unit includes a motor configured to drivethe annular imaging unit parallel with a central axis of the chamber. Ina seventh example of the system, optionally including one or more oreach of the first through sixth examples, the support surface includes amotor configured to drive the support surface parallel with a centralaxis of the chamber.

The disclosure also provides support for an imaging system, comprising:a base, an outer enclosure and an inner enclosure each supported by thebase, with the inner enclosure disposed within the outer enclosure andshaped to house a subject to be imaged, a subject support surfacearranged within the inner enclosure in direct contact with the base, animaging unit encircling the outer enclosure in a fixed angularorientation to the inner enclosure and including a distributed x-raysource unit and a detector array, and a cap sealing an end of the outerenclosure and an end of the inner enclosure opposite to the subjectsupport surface. In a first example of the system, the cap includes aplurality of illumination elements configured to emit ultravioletradiation. In a second example of the system, optionally including thefirst example, the base includes a plurality of openings fluidlycoupling an interior of the inner enclosure to a disinfectant source. Ina third example of the system, optionally including one or both of thefirst and second examples, the inner enclosure is fixed to the base andthe outer enclosure is rotatable relative to the inner enclosure and thebase. In a fourth example of the system, optionally including one ormore or each of the first through third examples, the inner enclosureincludes an opening shaped to receive the subject and having a firstarcuate length, and the outer enclosure has a second arcuate length thatis at least equal to the first arcuate length. In a fifth example of thesystem, optionally including one or more or each of the first throughfourth examples, in a rotated configuration, the outer enclosure sealsthe opening of the inner enclosure. In a sixth example of the system,optionally including one or more or each of the first through fifthexamples, the outer enclosure and the inner enclosure are formed from amaterial transparent to light having a wavelength within a range of400-750 nanometers.

The disclosure also provides support for a method, comprising: acquiringa scan of a subject supported in an upright position by: energizing adistributed x-ray source unit of an imaging system to emit x-rayradiation across an imaging chamber housing the subject, and receivingthe x-ray radiation at a detector array arranged opposite to thedistributed x-ray source unit, and while acquiring the scan of thesubject, maintaining an angular position of the distributed x-ray sourceunit relative to the imaging chamber. In a first example of the method,the method further comprises: while acquiring the scan of the subject,driving the distributed x-ray source unit and the detector array inunison in a vertical direction relative to a ground surface on which theimaging system sits. In a second example of the method, optionallyincluding the first example, the method further comprises: whileacquiring the scan of the subject, adjusting a position of the subjectwithin the imaging chamber via a motorized subject support surfacedisposed entirely within the imaging chamber. In a third example of themethod, optionally including one or both of the first and secondexamples, the method further comprises: following acquisition of thescan of the subject and while the subject is not within the imagingchamber, flowing disinfectant to the imaging chamber via a plurality ofopenings formed in a base supporting the imaging chamber. In a fourthexample of the method, optionally including one or more or each of thefirst through third examples, the method further comprises: followingacquisition of the scan of the subject and while the subject is notwithin the imaging chamber, emitting ultraviolet radiation into theimaging chamber by energizing a plurality of illumination elements of acap sealing the imaging chamber.

The disclosure also provides support for a method for a stationarycomputed tomography (CT) system, comprising: activating a plurality ofemitters of a stationary distributed x-ray source unit to emit x-raybeams toward an object within an imaging volume, where the x-ray sourceunit does not rotate around the imaging volume, receiving attenuatedx-ray beams with one or more detector arrays to form a sparse viewprojection dataset, where each attenuated x-ray beam generates adifferent view, and reconstructing an image from the sparse viewprojection dataset using a sparse view reconstruction method. In a firstexample of the method, reconstructing the image from the sparse viewprojection dataset using the sparse view reconstruction methodcomprises: entering the sparse view projection dataset into a generatortrained to output an artificial dense-view projection dataset, andreconstructing the image from the artificial dense-view projectiondataset. In a second example of the method, optionally including thefirst example, the generator is trained with a discriminator operatingin the image domain. In a third example of the method, optionallyincluding one or both of the first and second examples, training thegenerator comprises, for a training dataset comprising a real dense-viewdataset and a training sparse view dataset generated from the realdense-view dataset: entering the training sparse view dataset into thegenerator, reconstructing a first training image from a trainingartificial dense-view dataset output by the generator, reconstructing asecond training image from the real dense-view dataset, entering thefirst and second training images into the discriminator, and updatingthe generator based on output from the discriminator until thediscriminator cannot discriminate between the first training image andthe second training image. In a fourth example of the method, optionallyincluding one or more or each of the first through third examples,training the generator further comprises applying a loss function thatcompares the real dense-view dataset and the sparse view dataset or thatcompares the first training image to the second training image. In afifth example of the method, optionally including one or more or each ofthe first through fourth examples, the sparse view projection dataset isgenerated from 100 views or less and the real dense-view dataset isgenerated from approximately 1000 views. In a sixth example of themethod, optionally including one or more or each of the first throughfifth examples, reconstructing the image from the sparse view projectiondataset using the sparse view reconstruction method comprisesreconstructing the image from the sparse view projection dataset usingiterative reconstruction with one or more priors learned from one ormore deep learning networks, where each update stage of the iterativereconstruction includes a datafit update and a deep learning update. Ina seventh example of the method, optionally including one or more oreach of the first through sixth examples, reconstructing the image fromthe sparse view projection dataset using the sparse view reconstructionmethod comprises: entering the sparse view projection dataset into adeep learning network trained to output a first initial reconstructedimage, regularizing the first initial reconstructed image usingcompressed sensing to generate a second initial reconstructed image,updating the sparse view projection dataset based on an analytic mappingbetween the first initial reconstructed image and the second initialreconstructed image, entering the updated sparse view projection datasetinto the deep learning network to generate a third initial reconstructedimage, and iteratively refining the third initial reconstructed imagebased on the second initial reconstructed image to form a finalreconstructed image. In an eighth example of the method, optionallyincluding one or more or each of the first through seventh example,reconstructing the image from the sparse view projection dataset usingthe sparse view reconstruction method comprises: backprojecting eachview of the sparse view projection dataset to generate a separatesingle-view backprojection for each view, and entering each single-viewbackprojection as input to a deep learning network trained to output theimage. In a ninth example of the method, optionally including one ormore or each of the first through eighth examples, reconstructing theimage from the sparse view projection dataset using the sparse viewreconstruction method comprises reconstructing the image from the sparseview projection dataset using a hierarchical reconstruction method thatcomprises: partitioning the sparse view projection dataset into aplurality of densely-sampled view sets, entering each densely-sampledview set into a network trained to output a respective single view foreach densely-sampled view set, and reconstructing the image from eachrespective single view. In a tenth example of the method, optionallyincluding one or more or each of the first through ninth examples, themethod further comprises: prior to reconstructing the image, enteringthe sparse view projection dataset into a network trained to extrapolatemissing views in a view angle direction to form an extrapolated sparseview projection dataset, and reconstructing the image from theextrapolated sparse view projection dataset. In a eleventh example ofthe method, optionally including one or more or each of the firstthrough tenth examples, reconstructing the image from the sparse viewprojection dataset using the sparse view reconstruction methodcomprises: partitioning the sparse view projection dataset intotime-resolved subsets of views, separately reconstructing eachtime-resolved subset of views to generate a set of reconstructions,estimating motion of the object based on the set of reconstructions, andapplying a motion correction to the image based on the estimated motion,where the image is reconstructed from the sparse view projection datasetor the image is generated from the set of reconstructions. In a twelfthexample of the method, optionally including one or more or each of thefirst through eleventh examples, reconstructing the image from thesparse view projection dataset using the sparse view reconstructionmethod comprises: partitioning the sparse view projection dataset into afirst dataset comprising output from detector elements of the one ormore detector arrays positioned to intercept x-ray beams emitted from afirst subset of emitters of the plurality of emitters and a seconddataset comprising output from detector elements of the one or moredetector arrays positioned to intercept x-ray beams emitted from asecond subset of emitters of the plurality of emitters, the first set ofemitters having larger focal spots than the second set of emitters,reconstructing a first image from the first dataset using the sparseview reconstruction method, reconstructing a second image from thesecond dataset using the sparse view reconstruction method, andcombining the first image and the second image to form the image.

The disclosure also provides support for a stationary computedtomography (CT) system, comprising: an imaging unit comprising: one ormore stationary distributed x-ray source units each comprising aplurality of emitters positioned to emit x-ray beams through an imagingvolume, where the one or more x-ray source units do not rotate aroundthe imaging volume, and one or more detector arrays extending around atleast a portion of the imaging volume, each detector array comprising aplurality of detector elements, and one or more computing devicesconfigured to, during a scan of an object within the imaging volume:translate the imaging unit vertically along the object, activate eachplurality of emitters, sample each plurality of detector elements toobtain a projection dataset, and reconstruct one or more images from theprojection dataset using sparse view reconstruction method. In a firstexample of the method, reconstructing the one or more images from theprojection dataset using the sparse view reconstruction methodcomprises: partitioning the projection dataset into time-resolvedsubsets of views, separately reconstructing each time-resolved subset ofviews to generate a set of reconstructions, estimating motion of theobject based on the set of reconstructions, and applying a motioncorrection to an image of the one or more images based on the estimatedmotion, where the image is reconstructed from the projection dataset orthe image is generated from the set of reconstructions. In a secondexample of the method, optionally including the first example,reconstructing the one or more images from the projection dataset usingthe sparse view reconstruction method comprises: partitioning theprojection dataset into a first dataset comprising output from detectorelements positioned to intercept x-ray beams emitted from a first subsetof emitters and a second dataset comprising output from detectorelements positioned to intercept x-ray beams emitted from a secondsubset of emitters, the first subset of emitters having larger focalspots than the second subset of emitters, reconstructing a first imagefrom the first dataset using the sparse view reconstruction method,reconstructing a second image from the second dataset using the sparseview reconstruction method, and combining the first image and the secondimage to form a final image.

The disclosure also provides support for a method for a stationarycomputed tomography (CT) system, comprising: generating a sparse viewprojection dataset by activating a plurality of emitters of a stationarydistributed x-ray source unit to emit x-ray beams toward an objectwithin an imaging volume, where the x-ray source unit does not rotatearound the imaging volume, and receiving attenuated x-ray beams with oneor more detector arrays, the sparse view projection dataset differingfrom a dense view projection dataset in one or more of a total number ofviews, a spacing of views, a view angle range, and a field of view, andreconstructing an image from the sparse view projection dataset using asparse view reconstruction method that includes a deep learning networktrained with training data that includes: the dense view projectiondataset and/or one or more training images generated from the dense viewprojection dataset, and a pseudo sparse view projection datasetgenerated from the dense view projection dataset and/or one moretraining images generated from the pseudo sparse view projectiondataset, where the pseudo sparse view projection dataset is generated bydiscarding a plurality of views of the dense view projection dataset sothat a total number of views, a spacing of views, a view angle range,and a field of view of the pseudo sparse view dataset matches the totalnumber of views, the spacing of views, the view angle range, and thefield of view of the sparse view projection dataset. In a first exampleof the method, the total number of views of the sparse view projectiondataset is 100 views or less and the view angle range of the sparse viewprojection dataset is less than 180 degrees. In a second example of themethod, optionally including the first example, spacing of views of thesparse view projection dataset is non-uniform. In a third example of themethod, optionally including one or both of the first and secondexamples, reconstructing the image from the sparse view projectiondataset using the sparse view reconstruction method comprises:backprojecting each view of the sparse view projection dataset togenerate a separate single-view backprojection for each view, enteringeach single-view backprojection as input to the deep learning network,and receiving the image as output from the deep learning network.

The disclosure also provides support for a stationary computedtomography (CT) system, comprising: a stationary distributed x-raysource unit comprising a plurality of emitters positioned to emit x-raybeams through an imaging volume, one or more detector arrays extendingaround at least a portion of the imaging volume, each detector arraycomprising a plurality of detector elements, each detector elementconfigured to receive x-ray beams from more than one emitter, and ananti-scatter device configured to be positioned between one or moreemitters of the plurality of emitters and an object in the imagingvolume. In a first example of the system, each emitter is configured toemit a respective x-ray beam having a full fan-beam and wherein theanti-scatter device comprises a plurality of collimators each configuredto truncate a corresponding x-ray beam to form a partial fan-beam. In asecond example of the system, optionally including the first example,the plurality of emitters includes a first emitter, a second emitter,and a third emitter, and wherein the plurality of collimators comprisesa first collimator, a second collimator, and a third collimator, thefirst collimator positioned proximate the first emitter and configuredto truncate a first x-ray beam emitted from the first emitter to form afirst partial fan-beam having a first angular range, the secondcollimator positioned proximate the second emitter and configured totruncate a second x-ray beam emitted from the second emitter to form asecond partial fan-beam having a second angular range, and the thirdcollimator positioned proximate the third emitter and configured totruncate a third x-ray beam emitted from the third emitter to form athird partial fan-beam having a third angular range, the first angularrange different than the second angular range and the third angularrange and the second angular range different than the third angularrange. In a third example of the system, optionally including one orboth of the first and second examples, the x-ray source unit comprisesan x-ray source ring encircling the imaging volume with the plurality ofemitters positioned around the x-ray source ring, and wherein theanti-scatter device comprises a first plurality of collimatorspositioned around a first ring-shaped actuator and a second plurality ofcollimators positioned around a second ring-shaped actuator, and whereinthe first ring-shaped actuator and the second ring-shaped actuator aremovable to truncate one or more x-ray beams to form one or more partialfan-beams. In a fourth example of the system, optionally including oneor more or each of the first through third examples, each emitter isconfigured to emit a respective x-ray beam having a full fan-beam andwherein the anti-scatter device comprises a plurality of collimatorseach configured to break up a corresponding full fan-beam into a seriesof narrower fan-beams. In a fifth example of the system, optionallyincluding one or more or each of the first through fourth examples, theone or more detector arrays and the x-ray source unit are displacedalong a z-axis of the imaging volume, wherein each emitter is configuredto emit a respective x-ray beam having a full fan-beam, and wherein theanti-scatter device comprises one or more collimators each positionableto collimate a corresponding full fan-beam along the z-axis to form acollimated fan-beam that impinges on some but not all of a subset ofdetector elements of the one or more detector arrays along the z-axis.In a sixth example of the system, optionally including one or more oreach of the first through fifth examples, the system further comprises:a computing device configured to determine an amount of scatter based onoutput from the subset of the detector elements along the z-axis andcorrect output from all of the plurality of detector elements based onthe amount of scatter. In a seventh example of the system, optionallyincluding one or more or each of the first through sixth examples, thesystem further comprises: a source controller for triggering theplurality of emitters to emit the x-ray beams. In an eighth example ofthe system, optionally including one or more or each of the firstthrough seventh examples, at least a portion the emitters of theplurality of emitters are triggered simultaneously. In a ninth exampleof the system, optionally including one or more or each of the firstthrough eighth examples, each emitter of the plurality of emitters istriggered separately. In a tenth example of the system, optionallyincluding one or more or each of the first through ninth examples, thesystem further comprises: a computing device configured to reconstructone or more images from projection data acquired by the one or moredetector arrays upon the plurality of emitters being triggered to emitthe x-ray beams. In a eleventh example of the system, optionallyincluding one or more or each of the first through tenth examples, whenthe plurality of emitters is triggered, the x-ray source does not rotatearound the imaging volume. In a twelfth example of the system,optionally including one or more or each of the first through eleventhexamples, the x-ray source unit and the one or more detector arrays forman imaging unit configured to translate vertically along the imagingvolume when the plurality of emitters is triggered.

The disclosure also provides support for a method for a stationarycomputed tomography (CT) system, comprising: activating a plurality ofemitters of a stationary distributed x-ray source unit to emit x-raybeams toward an object within an imaging volume, where the x-ray sourceunit does not rotate around the imaging volume, collimating at least aportion of the x-ray beams to reduce scatter via an anti-scatter devicepositioned between the x-ray source unit and the object, receivingattenuated x-ray beams with one or more detector arrays, andreconstructing one or more images from projection data obtained from theone or more detector arrays. In a first example of the method, the x-raysource unit and the one or more detector arrays form an imaging unit,and further comprising translating the imaging unit vertically along theimaging volume while the plurality of emitters is activated. In a secondexample of the method, optionally including the first example,collimating at least the portion of the x-ray beams comprisescollimating a first x-ray beam emitted by a first emitter of theplurality of emitters to have a partial fan-beam with a first angularrange and collimating a second x-ray beam emitted by a second emitter ofthe plurality of emitters to have a partial fan-beam with a secondangular range that is different than the first angular range. In a thirdexample of the method, optionally including one or both of the first andsecond examples, collimating the first x-ray beam and collimating thesecond x-ray beam comprises adjusting a positon of a first ring-shapedactuator including a first plurality of collimators and/or adjusting apositon of a second ring-shaped actuator including a second plurality ofcollimators. In a fourth example of the method, optionally including oneor more or each of the first through third examples, collimating atleast the portion of the x-ray beams comprises collimating a first x-raybeam emitted by a first emitter of the plurality of emitters to form twoor more partial fan-beams.

The disclosure also provides support for a stationary computedtomography (CT) system, comprising: an imaging unit comprising: astationary distributed x-ray source unit comprising a plurality ofemitters positioned to emit x-ray beams through an imaging volume, wherethe x-ray source unit does not rotate around the imaging volume, one ormore detector arrays extending around at least a portion of the imagingvolume, each detector array comprising a plurality of detector elements,and an anti-scatter device comprising a plurality of collimators,wherein each x-ray beam is configured to be collimated by one or morecollimators of the plurality of collimators, and one or more computingdevices configured to, during a scan of an object within the imagingvolume, translate the imaging unit vertically along the object, activatethe plurality of emitters, sample the plurality of detector elements toobtain projection data, and reconstruct one or more images from theprojection data.

The disclosure also provides support for a method for a stationarycomputed tomography (CT) system, comprising: activating an emitter of aplurality of emitters of a stationary distributed x-ray source unit toemit an x-ray beam toward an object within an imaging volume, where thex-ray source unit does not rotate around the imaging volume, receivingthe x-ray beam at a subset of detector elements of a plurality ofdetector elements of one or more detector arrays, sampling the pluralityof detector elements to generate a total transmission profile, anattenuation profile, and a scatter measurement, generating ascatter-corrected attenuation profile by entering the total transmissionprofile, the attenuation profile, and the scatter measurement as inputsto a model, and reconstructing one or more images from thescatter-corrected attenuation profile. In a first example of the method,the total transmission profile is generated from detector output fromeach detector element of the plurality of detector elements, theattenuation profile is generated from output from only the subset ofdetector elements, and the scatter measurement is generated from outputfrom only one or more detector elements of the plurality of detectorelements outside the x-ray beam. In a second example of the method,optionally including the first example, the model is trained to outputthe scatter-corrected attenuation profile. In a third example of themethod, optionally including one or both of the first and secondexamples, the model is trained to output a scatter profile representingscatter of the x-ray beam detected by the plurality of detectorelements, and wherein generating the scatter-corrected attenuationprofile comprises correcting the attenuation profile with the scatterprofile to generate the scatter-corrected attenuation profile. In afourth example of the method, optionally including one or more or eachof the first through third examples, the model is trained with trainingdata pairs comprising, for a given view, scatter-corrupted data andscatter-reduced data. In a fifth example of the method, optionallyincluding one or more or each of the first through fourth examples, thescatter-corrupted data is acquired with a full fan-beam x-ray beam andthe scatter-reduced data is acquired with a partial fan-beam x-ray beam.In a sixth example of the method, optionally including one or more oreach of the first through fifth examples, the scatter-correctedattenuation profile represents a first view, and further comprisingactivating one or more additional emitters of the plurality of emittersto generate one or more additional attenuation profiles eachrepresenting a respective different additional view, scatter-correctingeach additional attenuation profile based on the scatter-correctedattenuation profile via interpolation to generate one or more additionalscatter-corrected attenuation profiles, and wherein reconstructing oneor more images from the scatter-corrected attenuation profile comprisesreconstructing one or more images from the scatter-corrected attenuationprofile and the one or more additional scatter-corrected attenuationprofiles.

The disclosure also provides support for a stationary computedtomography (CT) system, comprising: a stationary distributed x-raysource unit comprising a plurality of emitters positioned to emit x-raybeams toward an object in an imaging volume, a plurality of detectorelements forming one or more detector arrays extending around at least aportion of the imaging volume, and one or more computing devicesconfigured to: activate a first emitter of the plurality of emitters toemit a first x-ray beam shaped and positioned to be intercepted by asubset of detector elements of the plurality of detector elements,measure scatter of the first x-ray beam caused by the object, activateone or more additional emitters of the plurality of emitters to emit oneor more additional x-ray beams shaped and positioned to be interceptedby one or more additional subsets of detector elements of the pluralityof detector elements, obtain projection data from the subset of detectorelements and the one or more additional subsets of detector elements,correct the projection data with the measured scatter to formscatter-corrected projection data, and reconstruct one or more imagesfrom the scatter-corrected projection data. In a first example of thesystem, the first emitter is configured to emit the first x-ray beamwith a fan-beam spanning the subset of detector elements, and furthercomprising a lead blocker positioned proximate the first emitter, thelead blocker configured to attenuate a portion of the first x-ray beamin a center of the fan-beam such that a portion of detector elementswithin the subset of detector elements do not intercept the first x-raybeam, and wherein the scatter of the first x-ray beam caused by theobject is measured by the portion of the detector elements that do notintercept the first x-ray beam. In a second example of the system,optionally including the first example, the scatter of the first x-raybeam is measured by one or more detector elements outside the subset ofdetector elements that are not positioned to intercept the first x-raybeam. In a third example of the system, optionally including one or bothof the first and second examples, the system further comprises: amodulator positioned proximate the first emitter, the modulatorcomprising a plurality of attenuating blockers configured to attenuateportions of the first x-ray beam while not attenuating other portions ofthe first x-ray beam, and wherein the one or more computing devices areconfigured to measure the scatter of the first x-ray beam by samplingthe output from the subset of the detector elements and demodulating thesampled output to separate detector signals resulting from interceptionof the first x-ray beam and detector signals resulting from interceptionof the scatter. In a fourth example of the system, optionally includingone or more or each of the first through third examples, correcting theprojection data with the measured scatter to form scatter-correctedprojection data comprises entering the measured scatter and projectiondata from the subset of detector elements into a model trained toprovide a scatter estimation, and correcting the projection data fromthe subset of detector elements and the one or more additional subsetsof detector elements with the scatter estimation. In a fifth example ofthe system, optionally including one or more or each of the firstthrough fourth examples, correcting the projection data with themeasured scatter to form scatter-corrected projection data comprisesentering the measured scatter and projection data from the subset ofdetector elements into a model trained to provide scatter-correctedprojection data, and correcting projection data from the one or moreadditional subsets of detector elements based on the scatter-correctedprojection data via interpolation.

The disclosure also provides support for a method for a stationarycomputed tomography (CT) system, comprising: obtaining a plurality ofviews of projection data by sequentially activating a plurality ofemitters of a stationary distributed x-ray source unit to emit aplurality of x-ray beams toward an object within an imaging volume andintercepting the plurality of x-ray beams, after attenuation by theobject, at a plurality of detector elements of one or more detectorarrays, for a first view of the plurality of views obtained byactivating a first emitter of the plurality of emitters to emit aprimary x-ray beam, generating a transmission profile, an attenuationprofile, and a scatter measurement based on output from the plurality ofdetector elements, where the attenuation profile includes output fromonly detector elements positioned to intercept the primary x-ray beam,the scatter measurement includes output from only detector elementspositioned outside of the primary x-ray beam, and the transmissionprofile includes output from detector elements positioned to interceptthe primary x-ray beam and detector elements positioned outside of theprimary x-ray beam, entering the transmission profile, the attenuationprofile, and the scatter measurement into a model trained to output ascatter profile indicative of an amount of scattered x-ray beamsreceived at the detector elements positioned to intercept the primaryx-ray beam, correcting the projection data of the first view and eachremaining view based on the scatter profile, and reconstructing an imagefrom the corrected projection data. In a first example of the method,the x-ray source unit and the one or more detector arrays form animaging unit, and further comprising vertically translating the imagingunit while the plurality of emitters are sequentially activated. In asecond example of the method, optionally including the first example,reconstructing the image includes reconstructing the image using asparse view reconstruction method. In a third example of the method,optionally including one or both of the first and second examples, alead blocker is positioned proximate the first emitter such that theprimary x-ray beam is split into two separate x-ray beams and whereinthe detector elements positioned outside of the primary x-ray beaminclude detector elements positioned opposite the lead blocker such thatthe detector elements positioned to intercept the primary x-ray beam arepositioned on either side of the detector elements positioned outside ofthe primary x-ray beam.

The disclosure also provides support for a stationary computedtomography (CT) system, comprising: one or more detector arraysextending around at least a portion of an imaging volume, a stationarydistributed x-ray source unit, the x-ray source unit comprising aplurality of emitters including a first set of emitters configured tooperate at a first voltage and a second set of emitters configured tooperate at a second voltage, different than the first voltage, and asource controller for triggering the first set of emitters for acquiringfirst projection data by the one or more detector arrays and triggeringthe second set of emitters for acquiring second projection data by theone or more detector arrays, the first projection data and the secondprojection data usable to reconstruct one or more basis materialcomposition images or monochromatic images of an object within theimaging volume. In a first example of the system, the one or moredetector arrays comprise a detector ring that encircles the imagingvolume and the x-ray source unit comprises a first segment and a secondsegment, the first set of emitters positioned in the first segment andthe second set of emitters positioned in the second segment, the firstsegment forming a first semi-circle partially encircling the imagingvolume and the second segment forming a second semi-circle partiallyencircling the imaging volume. In a second example of the system,optionally including the first example, the one or more detector arrayscomprise a detector ring that encircles the imaging volume and the x-raysource unit comprises a first x-ray source ring and a second x-raysource ring each encircling the imaging volume, the first set ofemitters positioned in the first x-ray source ring and the second set ofemitters positioned in the second x-ray source ring. In a third exampleof the system, optionally including one or both of the first and secondexamples, the one or more detector arrays comprise a first detectorarray and a second detector array, wherein the x-ray source unitcomprises a first segment positioned opposite the imaging volume fromthe first detector array and a second segment positioned opposite theimaging volume from the second detector array, and wherein the first setof emitters is positioned in the first segment and the second set ofemitters is positioned in the second segment. In a fourth example of thesystem, optionally including one or more or each of the first throughthird examples, the system further comprises: a third detector array anda third segment of the x-ray source unit, the third segment positionedopposite the imaging volume from the third detector array, and whereinthe third segment includes a third set of emitters configured to operateat a third voltage, different than the first voltage and the secondvoltage. In a fifth example of the system, optionally including one ormore or each of the first through fourth examples, the one or moredetector arrays comprise a detector ring that encircles the imagingvolume and the x-ray source comprises an x-ray source ring encirclingthe imaging volume, the first set of emitters and the second set ofemitters positioned in an alternating fashion around the x-ray sourcering. In a sixth example of the system, optionally including one or moreor each of the first through fifth examples, when the first set ofemitters and the second set of emitters are triggered, the x-ray sourceunit does not rotate around the imaging volume and the one or moredetector arrays rotate around the imaging volume. In a seventh exampleof the system, optionally including one or more or each of the firstthrough sixth examples, at least a portion the emitters of the pluralityof emitters are triggered simultaneously. In a eighth example of thesystem, optionally including one or more or each of the first throughseventh examples, the system further comprises: a computing deviceconfigured to reconstruct one or more first images from the firstprojection data, reconstruct one or more second images from the secondprojection data, and generate the one or more basis material compositionimages or monochromatic images from the one or more first images and theone or more second images via a decomposition process. In a ninthexample of the system, optionally including one or more or each of thefirst through eighth examples, the first projection data comprises afirst set of views including a first view and the second projection datacomprises a second set of views including a second view adjacent to thefirst view, and further comprising a computing device configured toenter the first view and the second view as input to a network trainedto output a joint view, the one or more basis material compositionimages or monochromatic images reconstructed from the joint view. In atenth example of the system, optionally including one or more or each ofthe first through ninth examples, the system further comprises: a firstgenerator coupled to the first set of emitters and configured to supplythe first voltage and a second generator coupled to the second set ofemitters and configured to supply the second voltage.

The disclosure also provides support for a stationary computedtomography (CT) system, comprising: one or more detector arraysextending around at least a portion of an imaging volume, a stationarydistributed x-ray source unit, the x-ray source unit comprising aplurality of emitters configured to be switched between a first voltageand a second voltage, different than the first voltage, and a sourcecontroller for triggering the plurality of emitters at the first voltagefor acquiring first projection data by the one or more detector arraysand triggering the plurality of emitters at the second voltage foracquiring second projection data by the one or more detector arrays, thefirst projection data and the second projection data usable toreconstruct one or more basis material composition images ormonochromatic images of an object within the imaging volume. In a firstexample of the system, the first projection data and the secondprojection data are acquired sequentially, such that the sourcecontroller is configured to first trigger each emitter of the pluralityof emitters at the first voltage to acquire the first projection dataand then trigger each emitter of the plurality of emitters at the secondvoltage to acquire the second projection data. In a second example ofthe system, optionally including the first example, the first projectiondata and the second projection data are acquired in an interleavedmanner, such that the source controller is configured to trigger a firstemitter of the plurality of emitters at the first voltage and thenswitch the first emitter to the second voltage, and then trigger asecond emitter of the plurality of emitters at the first voltage andthen switch the second emitter to the second voltage. In a third exampleof the system, optionally including one or both of the first and secondexamples, the system further comprises: a dynamic resonanceenergy-recovery generator coupled to the x-ray source unit. In a fourthexample of the system, optionally including one or more or each of thefirst through third examples, each emitter comprises a cathode and ananode, each anode configured to be held at the first voltage and eachcathode configured to be switched from a negative voltage to ground inorder to switch that emitter to the second voltage. In a fifth exampleof the system, optionally including one or more or each of the firstthrough fourth examples, at least a portion of the emitters of theplurality of emitters are triggered simultaneously.

The disclosure also provides support for a method for a stationarycomputed tomography (CT) system, comprising: activating a plurality ofemitters of a stationary distributed x-ray source unit at a firstvoltage and at a second voltage to emit x-ray beams of a first energyand to emit x-ray beams of a second energy toward an object within animaging volume, where the x-ray source unit does not rotate around theimaging volume, receiving attenuated x-ray beams at the first energy andthe second energy with one or more detector arrays, and reconstructingone or more images from projection data obtained from the one or moredetector arrays. In a first example of the method, activating theplurality of emitters at the first voltage and the second voltagecomprises activating a first set of emitters of the plurality ofemitters at the first voltage to emit x-ray beams of the first energyand activating a second set of emitters of the plurality of emitters atthe second voltage to emit x-ray beams of the second energy. In a secondexample of the method, optionally including the first example,reconstructing the one or more images from the projection datacomprises: reconstructing one or more first images from first projectiondata obtained while x-ray beams of the first energy are emitted,reconstructing one or more second images from second projection dataobtained while x-ray beams of the second energy are emitted, andgenerating one or more basis material composition images ormonochromatic images from the one or more first images and the one ormore second images via a decomposition process.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “first,” “second,” andthe like, do not denote any order, quantity, or importance, but ratherare used to distinguish one element from another. The terms“comprising,” “including,” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. As the terms “connected to,” “coupled to,” etc. are usedherein, one object (e.g., a material, element, structure, member, etc.)can be connected to or coupled to another object regardless of whetherthe one object is directly connected or coupled to the other object orwhether there are one or more intervening objects between the one objectand the other object. In addition, it should be understood thatreferences to “one embodiment” or “an embodiment” of the presentdisclosure are not intended to be interpreted as excluding the existenceof additional embodiments that also incorporate the recited features.

In addition to any previously indicated modification, numerous othervariations and alternative arrangements may be devised by those skilledin the art without departing from the spirit and scope of thisdescription, and appended claims are intended to cover suchmodifications and arrangements. Thus, while the information has beendescribed above with particularity and detail in connection with what ispresently deemed to be the most practical and preferred aspects, it willbe apparent to those of ordinary skill in the art that numerousmodifications, including, but not limited to, form, function, manner ofoperation and use may be made without departing from the principles andconcepts set forth herein. Also, as used herein, the examples andembodiments, in all respects, are meant to be illustrative only andshould not be construed to be limiting in any manner.

1. A modular imaging system, comprising: a plurality of distributed x-ray source units releasably coupled to a plurality of detector arrays, with the plurality of distributed x-ray source units and the plurality of detector arrays forming a self-supporting structure including a central opening shaped to receive a subject to be imaged.
 2. The modular imaging system of claim 1, wherein each distributed x-ray source unit of the plurality of distributed x-ray source units is interchangeable with each other distributed x-ray source unit of the plurality of distributed x-ray source units and each detector array of the plurality of detector arrays is interchangeable with each other detector array of the plurality of detector arrays without altering an imaging quality of the modular imaging system.
 3. The modular imaging system of claim 1, wherein a central axis of the central opening extends parallel with a ground surface on which the self-supporting structure sits.
 4. The modular imaging system of claim 3, wherein a length from the central axis to each distributed x-ray source unit of the plurality of distributed x-ray source units is equal to a length from the central axis to each detector array of the plurality of detector arrays.
 5. The modular imaging system of claim 1, wherein the plurality of distributed x-ray source units consists of an odd number of distributed x-ray source units and the plurality of detector arrays consists of an odd number of detector arrays.
 6. The modular imaging system of claim 5, wherein the plurality of distributed x-ray source units includes exactly three distributed x-ray source units comprising a first distributed x-ray source unit, a second distributed x-ray source unit, and a third distributed x-ray source unit, and the plurality of detector arrays includes exactly three detector arrays comprising a first detector array, a second detector array, and a third detector array.
 7. The modular imaging system of claim 6, wherein a first axis extending along a centerline of the first distributed x-ray source unit is parallel with a second axis extending along a centerline of the first detector array, a third axis extending along a centerline of the second distributed x-ray source unit is parallel with fourth axis extending along a centerline of the second detector array, and a fifth axis extending along a centerline of the third distributed x-ray source unit is parallel with a sixth axis extending along a centerline of the third detector array.
 8. The modular imaging system of claim 1, wherein each distributed x-ray source unit of the plurality of distributed x-ray source units is arranged between two adjacent detector arrays of the plurality of detector arrays.
 9. The modular imaging system of claim 1, wherein each distributed x-ray source unit of the plurality of distributed x-ray source units is arranged in an alternating configuration with each detector array of the plurality of detector arrays.
 10. The modular imaging system of claim 1, wherein the self-supporting structure has a hexagonal profile.
 11. The modular imaging system of claim 1, wherein a length along a centerline of each distributed x-ray source unit of the plurality of distributed x-ray source units is equal to a length along a centerline of each detector array of the plurality of detector arrays.
 12. A portable imaging system, comprising: a first distributed x-ray source unit, a second distributed x-ray source unit, and a third distributed x-ray source unit; a first detector array arranged directly opposite to the first distributed x-ray source unit across a central axis of the portable imaging system and releaseably coupled to the second distributed x-ray source unit and the third distributed x-ray source unit; a second detector array arranged directly opposite to the second distributed x-ray source unit across the central axis and releaseably coupled to the first distributed x-ray source unit and the third distributed x-ray source unit; and a third detector array arranged directly opposite to the third distributed x-ray source unit across the central axis and releasably coupled to the first distributed x-ray source unit and the second distributed x-ray source unit.
 13. The portable imaging system of claim 12, wherein the first detector array releasably couples to the second distributed x-ray source unit and the third distributed x-ray source unit at a first angle relative to the second detector array and the third detector array, and the second detector array releasably couples to the first distributed x-ray source unit and the third distributed x-ray source unit at a second angle relative to the third detector array.
 14. The portable imaging system of claim 13, wherein the first angle is equal to the second angle.
 15. The portable imaging system of claim 12, wherein the first distributed x-ray source unit, the second distributed x-ray source unit, the third distributed x-ray source unit, the first detector array, the second detector array, and the third detector array are each vertically fixed within a same imaging plane relative to a ground surface on which the portable imaging system sits.
 16. The portable imaging system of claim 12, wherein the first distributed x-ray source unit, the second distributed x-ray source unit, the third distributed x-ray source unit, the second detector array, and the third detector array are each supported by the first detector array in a vertical direction relative to a ground surface on which the portable imaging system sits.
 17. A method, comprising: acquiring a scan of a subject via a modular imaging system by: energizing a first distributed x-ray source unit to emit x-ray radiation in a first direction and intercepting the x-ray radiation at a first detector array arranged opposite to the first distributed x-ray source unit; energizing a second distributed x-ray source unit to emit x-ray radiation in a second direction and intercepting the x-ray radiation at a second detector array arranged opposite to the second distributed x-ray source unit; and energizing a third distributed x-ray source unit to emit x-ray radiation in a third direction and intercepting the x-ray radiation at a third detector array arranged opposite to the third distributed x-ray source unit.
 18. The method of claim 17, further comprising releasably coupling the first distributed x-ray source unit to the second detector array and the third detector array, releasably coupling the second distributed x-ray source unit to the first detector array and the third detector array, and releasably coupling the third distributed x-ray source unit to the first detector array and the second detector array.
 19. The method of claim 17, further comprising, while acquiring the scan of the subject, maintaining the first distributed x-ray source unit vertically above the third detector array relative to a ground surface on which the modular imaging system sits throughout an entirety of the scan, maintaining the second distributed x-ray source unit vertically below the third detector array throughout the entirety of the scan, and maintaining the third distributed x-ray source unit vertically below the second detector array throughout the entirety of the scan.
 20. The method of claim 17, wherein energizing the first distributed x-ray source unit includes providing electrical energy to the first distributed x-ray source unit via a portable battery unit, energizing the second distributed x-ray source unit includes providing electrical energy to the second distributed x-ray source unit via the portable battery unit, and energizing the third distributed x-ray source unit includes providing electrical energy to the third distributed x-ray source unit via the portable battery unit. 